Dashboard refresh (logs, storage, network, object store, docs) (#835)

## Summary

This PR adds a session management service, several new dashboard pages, and a number of infrastructure improvements.

### Sessions Service
- `SessionsServiceClient` in `zenutil` announces sessions to a remote zenserver with a 15s heartbeat (POST/PUT/DELETE lifecycle)
- Storage server registers itself with its own local sessions service on startup
- Session mode attribute coupled to server mode (Compute, Proxy, Hub, etc.)
- Ended sessions tracked with `ended_at` timestamp; status filtering (Active/Ended/All)
- `--sessions-url` config option for remote session announcement
- In-process log sink (`InProcSessionLogSink`) forwards server log output to the server's own session, visible in the dashboard

### Session Log Viewer
- POST/GET endpoints for session logs (`/sessions/{id}/log`) supporting raw text and structured JSON/CbObject with batch `entries` array
- In-memory log storage per session (capped at 10k entries) with cursor-based pagination for efficient incremental fetching
- Log panel in the sessions dashboard with incremental DOM updates, auto-scroll (Follow toggle), newest-first toggle, text filter, and log-level coloring
- Auto-selects the server's own session on page load

### TCP Log Streaming
- `LogStreamListener` and `TcpLogStreamSink` for log delivery over TCP
- Sequence numbers on each message with drop detection and synthetic "dropped" notice on gaps
- Gathered buffer writes to reduce syscall overhead when flushing batches
- Tests covering basic delivery, multi-line splitting, drop detection, and sequencing

### New Dashboard Pages
- **Sessions**: master-detail layout with selectable rows, metadata panel, live WebSocket updates, paging, abbreviated date formatting, and "this" pill for the local session
- **Object Store**: summary stats tiles and bucket table with click-to-expand inline object listing (`GET /obj/`)
- **Storage**: per-volume disk usage breakdown (`GET /admin/storage`), Garbage Collection status section (next-run countdown, last-run stats), and GC History table with paginated rows and expandable detail panels
- **Network**: overview tiles, per-service request table, proxy connections, and live WebSocket updates; distinct client IPs and session counts via HyperLogLog

### Documentation Page
- In-dashboard Docs page with sidebar navigation, markdown rendering (via `marked`), Mermaid diagram support (theme-aware), collapsible sections, text filtering with highlighting, and cross-document linking
- New user-facing docs: `overview.md` (with architecture and per-mode diagrams), `sessions.md`, `cache.md`, `projects.md`; updated `compute.md`
- Dev docs moved to `docs/dev/`

### Infrastructure & Bug Fixes
- **Deflate compression** for the embedded frontend zip (~3.4MB → ~950KB); zlib inflate support added to `ZipFs` with cached decompressed buffers
- **Local IP addresses**: `GetLocalIpAddresses()` (Windows via `GetAdaptersAddresses`, Linux/Mac via `getifaddrs`); surfaced in `/status/status`, `/health/info`, and the dashboard banner
- **Dashboard nav**: unified into `zen-nav` web component with `MutationObserver` for dynamically added links, CSS `::part()` to merge banner/nav border radii, and prefix-based active link detection
- Stats broadcast refactored from manual JSON string concatenation to `CbObjectWriter`; `CbObject`-to-JS conversion improved for `TimeSpan`, `DateTime`, and large integers
- Stats WebSocket boilerplate consolidated into `ZenPage.connect_stats_ws()`

7 files changed, 327 insertions, 5 deletions

diff --git a/src/zenserver/storage/admin/admin.cpp b/src/zenserver/storage/admin/admin.cpp
index 6e78a6179..f1c2daea4 100644
--- a/src/zenserver/storage/admin/admin.cpp
+++ b/src/zenserver/storage/admin/admin.cpp
@@ -791,6 +791,139 @@ HttpAdminService::HttpAdminService(GcScheduler&			   Scheduler,
 		},
 		HttpVerb::kPost);
 	m_Router.RegisterRoute(
+		"storage",
+		[this](HttpRouterRequest& Req) {
+			CbObjectWriter Obj;
+
+			// Collect known storage directories
+			struct StorageDir
+			{
+				std::string_view	  Name;
+				std::filesystem::path Path;
+			};
+
+			std::vector<StorageDir>		 Dirs;
+			const std::filesystem::path& DataDir = m_ServerOptions.DataDir;
+			Dirs.push_back({"cache"sv, DataDir / "cache"});
+			Dirs.push_back({"cas"sv, DataDir / "cas"});
+			Dirs.push_back({"projects"sv, DataDir / "projects"});
+			Dirs.push_back({"builds"sv, DataDir / "builds"});
+			Dirs.push_back({"builds_cas"sv, DataDir / "builds_cas"});
+			Dirs.push_back({"obj"sv, DataDir / "obj"});
+
+			// Group directories by volume (identified by total capacity)
+			struct VolumeInfo
+			{
+				DiskSpace					   Space;
+				std::vector<const StorageDir*> Directories;
+			};
+
+			// Use canonical path to identify volumes. Directories on the same volume
+			// will report the same total capacity from DiskSpaceInfo.
+			std::vector<VolumeInfo> Volumes;
+			auto					FindOrAddVolume = [&](DiskSpace Space) -> VolumeInfo& {
+				   for (VolumeInfo& V : Volumes)
+				   {
+					   if (V.Space.Total == Space.Total && V.Space.Free == Space.Free)
+					   {
+						   return V;
+					   }
+				   }
+				   Volumes.push_back({Space, {}});
+				   return Volumes.back();
+			};
+
+			for (StorageDir& Dir : Dirs)
+			{
+				if (!IsDir(Dir.Path))
+				{
+					continue;
+				}
+				DiskSpace Space;
+				if (DiskSpaceInfo(Dir.Path, Space))
+				{
+					FindOrAddVolume(Space).Directories.push_back(&Dir);
+				}
+			}
+
+			Obj.BeginArray("volumes"sv);
+			for (const VolumeInfo& Vol : Volumes)
+			{
+				Obj.BeginObject();
+				Obj << "total"sv << Vol.Space.Total;
+				Obj << "free"sv << Vol.Space.Free;
+				Obj << "used"sv << (Vol.Space.Total - Vol.Space.Free);
+
+				Obj.BeginArray("directories"sv);
+				for (const StorageDir* Dir : Vol.Directories)
+				{
+					Obj.BeginObject();
+					Obj << "name"sv << Dir->Name;
+					Obj << "path"sv << Dir->Path.string();
+
+					DirStats Stats = GetStatsForDirectory(Dir->Path);
+					Obj << "bytes"sv << Stats.ByteCount;
+					Obj << "files"sv << Stats.FileCount;
+					Obj.EndObject();
+				}
+				Obj.EndArray();
+				Obj.EndObject();
+			}
+			Obj.EndArray();
+
+			Req.ServerRequest().WriteResponse(HttpResponseCode::OK, Obj.Save());
+		},
+		HttpVerb::kGet);
+
+	m_Router.RegisterRoute(
+		"gclog",
+		[this](HttpRouterRequest& Req) {
+			const GcSchedulerState		State = m_GcScheduler.GetState();
+			const std::filesystem::path Path  = State.Config.RootDirectory / "gc.log";
+
+			CbObjectWriter Response;
+			Response.BeginArray("entries"sv);
+
+			try
+			{
+				if (IsFile(Path))
+				{
+					IoBuffer FileData = ReadFile(Path).Flatten();
+
+					// The log file contains concatenated named CBO object fields.
+					// Each field is a complete entry: [type+name header][object payload].
+					// We wrap each one in a CbObject and add it to the response array.
+					const uint8_t* Ptr = static_cast<const uint8_t*>(FileData.GetData());
+					const uint8_t* End = Ptr + FileData.GetSize();
+
+					while (Ptr < End)
+					{
+						CbFieldView Field(Ptr);
+						uint64_t	FieldSize = Field.GetSize();
+						if (FieldSize == 0 || Ptr + FieldSize > End)
+						{
+							break;
+						}
+
+						// Wrap the named field as an object and add it
+						CbObjectView ObjView = Field.AsObjectView();
+						CbObject	 Entry	 = CbObject::Clone(ObjView);
+						Response.AddObject(Entry);
+						Ptr += FieldSize;
+					}
+				}
+			}
+			catch (const std::exception& Ex)
+			{
+				ZEN_WARN("failed to read gc log '{}': {}", Path, Ex.what());
+			}
+
+			Response.EndArray();
+			Req.ServerRequest().WriteResponse(HttpResponseCode::OK, Response.Save());
+		},
+		HttpVerb::kGet);
+
+	m_Router.RegisterRoute(
 		"flush",
 		[this](HttpRouterRequest& Req) {
 			HttpServerRequest& HttpReq = Req.ServerRequest();
diff --git a/src/zenserver/storage/objectstore/objectstore.cpp b/src/zenserver/storage/objectstore/objectstore.cpp
index e347e2dfe..493326a32 100644
--- a/src/zenserver/storage/objectstore/objectstore.cpp
+++ b/src/zenserver/storage/objectstore/objectstore.cpp
@@ -280,6 +280,16 @@ HttpObjectStoreService::Inititalize()
 						[](std::string_view Str) -> bool { return !Str.empty() && AsciiSet::HasOnly(Str, ValidBucketCharactersSet); });
 
 	m_Router.RegisterRoute(
+		"",
+		[this](zen::HttpRouterRequest& Request) { ListBuckets(Request); },
+		HttpVerb::kGet);
+
+	m_Router.RegisterRoute(
+		"bucket",
+		[this](zen::HttpRouterRequest& Request) { ListBuckets(Request); },
+		HttpVerb::kGet);
+
+	m_Router.RegisterRoute(
 		"bucket",
 		[this](zen::HttpRouterRequest& Request) { CreateBucket(Request); },
 		HttpVerb::kPost | HttpVerb::kPut);
@@ -332,6 +342,98 @@ HttpObjectStoreService::GetBucketDirectory(std::string_view BucketName)
 }
 
 void
+HttpObjectStoreService::ListBuckets(zen::HttpRouterRequest& Request)
+{
+	namespace fs = std::filesystem;
+
+	const fs::path BucketsPath = m_Cfg.RootDirectory / "buckets";
+
+	CbObjectWriter Response;
+	Response.BeginArray("buckets");
+	{
+		std::lock_guard _(BucketsMutex);
+
+		// Configured buckets
+		for (const ObjectStoreConfig::BucketConfig& Bucket : m_Cfg.Buckets)
+		{
+			Response.BeginObject();
+			Response << "name" << Bucket.Name;
+
+			const fs::path Dir = Bucket.Directory.empty() ? (m_Cfg.RootDirectory / Bucket.Name) : Bucket.Directory;
+			if (IsDir(Dir))
+			{
+				uint64_t TotalSize = 0;
+				uint64_t FileCount = 0;
+				for (const fs::directory_entry& Entry :
+					 fs::recursive_directory_iterator(Dir, fs::directory_options::skip_permission_denied))
+				{
+					if (Entry.is_regular_file())
+					{
+						TotalSize += Entry.file_size();
+						FileCount++;
+					}
+				}
+				Response << "size" << TotalSize;
+				Response << "object_count" << FileCount;
+			}
+			Response.EndObject();
+		}
+
+		// Dynamic buckets (on-disk directories not in config)
+		if (IsDir(BucketsPath))
+		{
+			for (const fs::directory_entry& Entry : fs::directory_iterator(BucketsPath))
+			{
+				if (!Entry.is_directory())
+				{
+					continue;
+				}
+				const std::string Name = Entry.path().filename().string();
+
+				// Skip if already listed as a configured bucket
+				bool IsConfigured = false;
+				for (const ObjectStoreConfig::BucketConfig& Bucket : m_Cfg.Buckets)
+				{
+					if (Bucket.Name == Name)
+					{
+						IsConfigured = true;
+						break;
+					}
+				}
+				if (IsConfigured)
+				{
+					continue;
+				}
+
+				Response.BeginObject();
+				Response << "name" << Name;
+
+				uint64_t TotalSize = 0;
+				uint64_t FileCount = 0;
+				for (const fs::directory_entry& FileEntry :
+					 fs::recursive_directory_iterator(Entry.path(), fs::directory_options::skip_permission_denied))
+				{
+					if (FileEntry.is_regular_file())
+					{
+						TotalSize += FileEntry.file_size();
+						FileCount++;
+					}
+				}
+				Response << "size" << TotalSize;
+				Response << "object_count" << FileCount;
+
+				Response.EndObject();
+			}
+		}
+	}
+	Response.EndArray();
+
+	Response << "total_bytes_served" << TotalBytesServed.load();
+
+	return Request.ServerRequest().WriteResponse(HttpResponseCode::OK, Response.Save());
+}
+
+void
 HttpObjectStoreService::CreateBucket(zen::HttpRouterRequest& Request)
 {
 	namespace fs = std::filesystem;
diff --git a/src/zenserver/storage/objectstore/objectstore.h b/src/zenserver/storage/objectstore/objectstore.h
index 44e50e208..cc47b50c4 100644
--- a/src/zenserver/storage/objectstore/objectstore.h
+++ b/src/zenserver/storage/objectstore/objectstore.h
@@ -37,6 +37,7 @@ public:
 private:
 	void				  Inititalize();
 	std::filesystem::path GetBucketDirectory(std::string_view BucketName);
+	void				  ListBuckets(zen::HttpRouterRequest& Request);
 	void				  CreateBucket(zen::HttpRouterRequest& Request);
 	void				  ListBucket(zen::HttpRouterRequest& Request, const std::string_view Path);
 	void				  DeleteBucket(zen::HttpRouterRequest& Request);
diff --git a/src/zenserver/storage/storageconfig.cpp b/src/zenserver/storage/storageconfig.cpp
index e8ccb9097..0dbb45164 100644
--- a/src/zenserver/storage/storageconfig.cpp
+++ b/src/zenserver/storage/storageconfig.cpp
@@ -373,6 +373,7 @@ ZenStorageServerConfigurator::AddConfigOptions(LuaConfig::Options& LuaOptions)
 
 	////// server
 	LuaOptions.AddOption("server.pluginsconfigfile"sv, ServerOptions.PluginsConfigFile, "plugins-config"sv);
+	LuaOptions.AddOption("sessions.url"sv, ServerOptions.SessionsTargetUrl, "sessions-url"sv);
 
 	////// objectstore
 	LuaOptions.AddOption("server.objectstore.enabled"sv, ServerOptions.ObjectStoreEnabled, "objectstore-enabled"sv);
@@ -620,6 +621,8 @@ ZenStorageServerCmdLineOptions::AddCliOptions(cxxopts::Options& options, ZenStor
 						  cxxopts::value(ServerOptions.ScrubOptions)->implicit_value("yes"),
 						  "(nocas,nogc,nodelete,yes,no)*");
 
+	options.add_options()("sessions-url", "URL of remote zenserver to announce session to", cxxopts::value<std::string>(SessionsTargetUrl));
+
 	AddSecurityOptions(options, ServerOptions);
 	AddCacheOptions(options, ServerOptions);
 	AddGcOptions(options, ServerOptions);
@@ -1069,6 +1072,7 @@ ZenStorageServerCmdLineOptions::ApplyOptions(cxxopts::Options& options, ZenStora
 			{.Name = OpenIdProviderName, .Url = OpenIdProviderUrl, .ClientId = OpenIdClientId});
 	}
 
+	ServerOptions.SessionsTargetUrl	  = SessionsTargetUrl;
 	ServerOptions.ObjectStoreConfig	  = ParseBucketConfigs(BucketConfigs);
 	ServerOptions.OidcTokenExecutable = MakeSafeAbsolutePath(OidcTokenExecutable);
 }
diff --git a/src/zenserver/storage/storageconfig.h b/src/zenserver/storage/storageconfig.h
index 128804d92..18af4f096 100644
--- a/src/zenserver/storage/storageconfig.h
+++ b/src/zenserver/storage/storageconfig.h
@@ -162,6 +162,7 @@ struct ZenStorageServerConfig : public ZenServerConfig
 	bool					 RestrictContentTypes = false;
 	std::filesystem::path	 OidcTokenExecutable;
 	bool					 AllowExternalOidcTokenExe = true;
+	std::string				 SessionsTargetUrl;
 };
 
 struct ZenStorageServerCmdLineOptions
@@ -183,6 +184,8 @@ struct ZenStorageServerCmdLineOptions
 
 	void AddSecurityOptions(cxxopts::Options& options, ZenStorageServerConfig& ServerOptions);
 
+	std::string SessionsTargetUrl;
+
 	std::string UpstreamCachePolicyOptions;
 
 	void AddCacheOptions(cxxopts::Options& options, ZenStorageServerConfig& ServerOptions);
diff --git a/src/zenserver/storage/zenstorageserver.cpp b/src/zenserver/storage/zenstorageserver.cpp
index 68d722f60..de00eb1c2 100644
--- a/src/zenserver/storage/zenstorageserver.cpp
+++ b/src/zenserver/storage/zenstorageserver.cpp
@@ -34,9 +34,11 @@
 #include <zentelemetry/otlptrace.h>
 #include <zenutil/logging.h>
 #include <zenutil/service.h>
+#include <zenutil/sessionsclient.h>
 #include <zenutil/workerpools.h>
 #include <zenutil/zenserverprocess.h>
-#include "../sessions/sessions.h"
+#include "sessions/inprocsessionlogsink.h"
+#include "sessions/sessions.h"
 
 #if ZEN_PLATFORM_WINDOWS
 #	include <zencore/windows.h>
@@ -251,7 +253,22 @@ ZenStorageServer::InitializeServices(const ZenStorageServerConfig& ServerOptions
 
 	{
 		m_SessionsService	  = std::make_unique<SessionsService>();
-		m_HttpSessionsService = std::make_unique<HttpSessionsService>(m_StatusService, m_StatsService, *m_SessionsService);
+		m_HttpSessionsService = std::make_unique<HttpSessionsService>(m_StatusService, m_StatsService, *m_SessionsService, m_IoContext);
+		m_HttpSessionsService->SetSelfSessionId(GetSessionId());
+
+		m_InProcSessionLogSink = logging::SinkPtr(new InProcSessionLogSink(*m_SessionsService));
+		m_InProcSessionLogSink->SetLevel(logging::Info);
+		GetDefaultBroadcastSink()->AddSink(m_InProcSessionLogSink);
+	}
+
+	if (!ServerOptions.SessionsTargetUrl.empty())
+	{
+		m_SessionsClient = std::make_unique<SessionsServiceClient>(SessionsServiceClient::Options{
+			.TargetUrl = ServerOptions.SessionsTargetUrl,
+			.AppName   = "zenserver",
+			.Mode	   = GetServerMode(),
+			.SessionId = GetSessionId(),
+		});
 	}
 
 	if (ServerOptions.BuildStoreConfig.Enabled)
@@ -821,6 +838,17 @@ ZenStorageServer::Run()
 
 	OnReady();
 
+	m_SessionsService->RegisterSession(GetSessionId(), "zenserver", GetServerMode(), Oid::Zero, {});
+
+	if (m_SessionsClient)
+	{
+		(void)m_SessionsClient->Announce();
+		EnqueueSessionAnnounceTimer();
+
+		m_SessionLogSink = m_SessionsClient->CreateLogSink();
+		GetDefaultBroadcastSink()->AddSink(m_SessionLogSink);
+	}
+
 	if (m_IsPowerCycle)
 	{
 		ZEN_INFO("Power cycle mode enabled -- shutting down");
@@ -841,19 +869,48 @@ ZenStorageServer::Cleanup()
 	ZEN_INFO(ZEN_APP_NAME " cleaning up");
 	try
 	{
+		m_SessionAnnounceTimer.cancel();
+
+		// Stop the IO context and join its thread first, before removing sinks.
+		// This ensures no async operations are trying to log through the
+		// broadcast sink while we modify its sink list.
 		m_IoContext.stop();
 		if (m_IoRunner.joinable())
 		{
 			m_IoRunner.join();
 		}
 
-		ShutdownServices();
-
+		// Close the HTTP server before removing sinks. HTTP worker threads
+		// continuously log messages and hold the BroadcastSink shared lock,
+		// which would starve the exclusive lock needed by RemoveSink().
 		if (m_Http)
 		{
 			m_Http->Close();
 		}
 
+		if (m_InProcSessionLogSink)
+		{
+			GetDefaultBroadcastSink()->RemoveSink(m_InProcSessionLogSink);
+			m_InProcSessionLogSink = {};
+		}
+		if (m_SessionLogSink)
+		{
+			GetDefaultBroadcastSink()->RemoveSink(m_SessionLogSink);
+			m_SessionLogSink = {};
+		}
+		if (m_SessionsClient)
+		{
+			(void)m_SessionsClient->Remove();
+			m_SessionsClient.reset();
+		}
+
+		if (m_SessionsService)
+		{
+			m_SessionsService->RemoveSession(GetSessionId());
+		}
+
+		ShutdownServices();
+
 		if (m_JobQueue)
 		{
 			m_JobQueue->Stop();
@@ -938,6 +995,20 @@ ZenStorageServer::CheckStateMarker()
 }
 
 void
+ZenStorageServer::EnqueueSessionAnnounceTimer()
+{
+	m_SessionAnnounceTimer.expires_after(std::chrono::seconds(15));
+	m_SessionAnnounceTimer.async_wait([this](const asio::error_code& Ec) {
+		if (!Ec && m_SessionsClient)
+		{
+			(void)m_SessionsClient->Announce();
+			EnqueueSessionAnnounceTimer();
+		}
+	});
+	EnsureIoRunner();
+}
+
+void
 ZenStorageServer::Flush()
 {
 	ZEN_TRACE_CPU("ZenStorageServer::Flush");
diff --git a/src/zenserver/storage/zenstorageserver.h b/src/zenserver/storage/zenstorageserver.h
index d625f869c..fad22ad54 100644
--- a/src/zenserver/storage/zenstorageserver.h
+++ b/src/zenserver/storage/zenstorageserver.h
@@ -12,7 +12,6 @@
 #include <zenstore/gc.h>
 #include <zenstore/projectstore.h>
 
-#include "../sessions/httpsessions.h"
 #include "admin/admin.h"
 #include "buildstore/httpbuildstore.h"
 #include "cache/httpstructuredcache.h"
@@ -20,11 +19,14 @@
 #include "frontend/frontend.h"
 #include "objectstore/objectstore.h"
 #include "projectstore/httpprojectstore.h"
+#include "sessions/httpsessions.h"
 #include "stats/statsreporter.h"
 #include "upstream/upstream.h"
 #include "vfs/vfsservice.h"
 #include "workspaces/httpworkspaces.h"
 
+#include <zenutil/sessionsclient.h>
+
 #if ZEN_WITH_COMPUTE_SERVICES
 #	include <zencompute/httpcomputeservice.h>
 #endif
@@ -94,6 +96,12 @@ private:
 	std::unique_ptr<HttpAdminService>			m_AdminService;
 	std::unique_ptr<HttpApiService>				m_ApiService;
 
+	std::unique_ptr<SessionsServiceClient> m_SessionsClient;
+	logging::SinkPtr					   m_SessionLogSink;
+	logging::SinkPtr					   m_InProcSessionLogSink;
+	asio::steady_timer					   m_SessionAnnounceTimer{m_IoContext};
+	void								   EnqueueSessionAnnounceTimer();
+
 #if ZEN_WITH_COMPUTE_SERVICES
 	std::unique_ptr<compute::HttpComputeService> m_HttpComputeService;
 #endif