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, 57 insertions, 10 deletions

diff --git a/src/zenserver/frontend/zipfs.cpp b/src/zenserver/frontend/zipfs.cpp
index 42df0520f..c7c8687ca 100644
--- a/src/zenserver/frontend/zipfs.cpp
+++ b/src/zenserver/frontend/zipfs.cpp
@@ -2,6 +2,12 @@
 
 #include "zipfs.h"
 
+#include <zencore/logging.h>
+
+ZEN_THIRD_PARTY_INCLUDES_START
+#include <zlib.h>
+ZEN_THIRD_PARTY_INCLUDES_END
+
 namespace zen {
 
 //////////////////////////////////////////////////////////////////////////
@@ -126,15 +132,20 @@ ZipFs::ZipFs(IoBuffer&& Buffer)
 		const CentralDirectoryRecord& Cd = *CdCursor;
 
 		bool Acceptable = true;
-		Acceptable &= (Cd.OriginalSize > 0);		// has some content
-		Acceptable &= (Cd.CompressionMethod == 0);	// is stored uncomrpessed
+		Acceptable &= (Cd.OriginalSize > 0);									 // has some content
+		Acceptable &= (Cd.CompressionMethod == 0 || Cd.CompressionMethod == 8);	 // stored or deflate
 		if (Acceptable)
 		{
 			const uint8_t* Lfh = Cursor + Cd.Offset;
 			if (uintptr_t(Lfh - Cursor) < View.GetSize())
 			{
 				std::string_view FileName(Cd.FileName, Cd.FileNameLength);
-				m_Files.insert(std::make_pair(FileName, FileItem{Lfh, size_t(0)}));
+				FileItem		 Item;
+				Item.View			   = MemoryView{Lfh, size_t(0)};
+				Item.CompressionMethod = Cd.CompressionMethod;
+				Item.CompressedSize	   = Cd.CompressedSize;
+				Item.UncompressedSize  = Cd.OriginalSize;
+				m_Files.insert(std::make_pair(FileName, std::move(Item)));
 			}
 		}
 
@@ -159,23 +170,59 @@ ZipFs::GetFile(const std::string_view& FileName) const
 		}
 
 		const FileItem& Item = Iter->second;
-		if (Item.GetSize() > 0)
+		if (Item.View.GetSize() > 0)
 		{
-			return IoBuffer(IoBuffer::Wrap, Item.GetData(), Item.GetSize());
+			return IoBuffer(IoBuffer::Wrap, Item.View.GetData(), Item.View.GetSize());
 		}
 	}
 
 	RwLock::ExclusiveLockScope _(m_FilesLock);
 
 	FileItem& Item = m_Files.find(FileName)->second;
-	if (Item.GetSize() > 0)
+	if (Item.View.GetSize() > 0)
+	{
+		return IoBuffer(IoBuffer::Wrap, Item.View.GetData(), Item.View.GetSize());
+	}
+
+	const auto*	   Lfh		= (LocalFileHeader*)(Item.View.GetData());
+	const uint8_t* FileData = (const uint8_t*)(Lfh->FileName + Lfh->FileNameLength + Lfh->ExtraFieldLength);
+
+	if (Item.CompressionMethod == 0)
+	{
+		// Stored — point directly into the buffer
+		Item.View = MemoryView(FileData, Item.UncompressedSize);
+	}
+	else
 	{
-		return IoBuffer(IoBuffer::Wrap, Item.GetData(), Item.GetSize());
+		// Deflate — decompress using zlib
+		Item.DecompressedData = IoBuffer(Item.UncompressedSize);
+
+		z_stream Stream	 = {};
+		Stream.next_in	 = const_cast<Bytef*>(FileData);
+		Stream.avail_in	 = Item.CompressedSize;
+		Stream.next_out	 = (Bytef*)Item.DecompressedData.GetMutableView().GetData();
+		Stream.avail_out = Item.UncompressedSize;
+
+		// Use raw inflate (-MAX_WBITS) since zip stores raw deflate streams
+		if (inflateInit2(&Stream, -MAX_WBITS) != Z_OK)
+		{
+			ZEN_WARN("failed to initialize inflate for '{}'", FileName);
+			return {};
+		}
+
+		int Result = inflate(&Stream, Z_FINISH);
+		inflateEnd(&Stream);
+
+		if (Result != Z_STREAM_END)
+		{
+			ZEN_WARN("failed to decompress '{}' (zlib error {})", FileName, Result);
+			return {};
+		}
+
+		Item.View = Item.DecompressedData.GetView();
 	}
 
-	const auto* Lfh = (LocalFileHeader*)(Item.GetData());
-	Item			= MemoryView(Lfh->FileName + Lfh->FileNameLength + Lfh->ExtraFieldLength, Lfh->OriginalSize);
-	return IoBuffer(IoBuffer::Wrap, Item.GetData(), Item.GetSize());
+	return IoBuffer(IoBuffer::Wrap, Item.View.GetData(), Item.View.GetSize());
 }
 
 }  // namespace zen