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()`

1 files changed, 102 insertions, 0 deletions

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;