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, 214 insertions, 0 deletions

diff --git a/src/zenserver/frontend/zipfs_test.cpp b/src/zenserver/frontend/zipfs_test.cpp
new file mode 100644
index 000000000..b5937b71c
--- /dev/null
+++ b/src/zenserver/frontend/zipfs_test.cpp
@@ -0,0 +1,214 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#include "zipfs.h"
+
+#include <zencore/iobuffer.h>
+
+#if ZEN_WITH_TESTS
+
+ZEN_THIRD_PARTY_INCLUDES_START
+#	include <doctest/doctest.h>
+#	include <zlib.h>
+ZEN_THIRD_PARTY_INCLUDES_END
+
+#	include <cstring>
+#	include <vector>
+
+TEST_SUITE_BEGIN("server.zipfs");
+
+namespace {
+
+// Helpers to build a minimal zip file in memory
+struct ZipBuilder
+{
+	std::vector<uint8_t> Data;
+
+	struct Entry
+	{
+		std::string Name;
+		uint32_t	LocalHeaderOffset;
+		uint16_t	CompressionMethod;
+		uint32_t	CompressedSize;
+		uint32_t	UncompressedSize;
+	};
+
+	std::vector<Entry> Entries;
+
+	void Append(const void* Src, size_t Size)
+	{
+		const uint8_t* Bytes = (const uint8_t*)Src;
+		Data.insert(Data.end(), Bytes, Bytes + Size);
+	}
+
+	void AppendU16(uint16_t V) { Append(&V, 2); }
+	void AppendU32(uint32_t V) { Append(&V, 4); }
+
+	void AddFile(const std::string& Name, const void* Content, size_t ContentSize, bool Deflate)
+	{
+		std::vector<uint8_t> FileData;
+		uint16_t			 Method = 0;
+
+		if (Deflate)
+		{
+			// Compress with raw deflate (no zlib/gzip header)
+			uLongf				 BoundSize = compressBound((uLong)ContentSize);
+			std::vector<uint8_t> TempBuf(BoundSize);
+
+			z_stream Stream	 = {};
+			Stream.next_in	 = (Bytef*)Content;
+			Stream.avail_in	 = (uInt)ContentSize;
+			Stream.next_out	 = TempBuf.data();
+			Stream.avail_out = (uInt)TempBuf.size();
+
+			deflateInit2(&Stream, Z_DEFAULT_COMPRESSION, Z_DEFLATED, -MAX_WBITS, 8, Z_DEFAULT_STRATEGY);
+			deflate(&Stream, Z_FINISH);
+			deflateEnd(&Stream);
+
+			TempBuf.resize(Stream.total_out);
+			FileData = std::move(TempBuf);
+			Method	 = 8;
+		}
+		else
+		{
+			FileData.assign((const uint8_t*)Content, (const uint8_t*)Content + ContentSize);
+		}
+
+		Entry E;
+		E.Name				= Name;
+		E.LocalHeaderOffset = (uint32_t)Data.size();
+		E.CompressionMethod = Method;
+		E.CompressedSize	= (uint32_t)FileData.size();
+		E.UncompressedSize	= (uint32_t)ContentSize;
+		Entries.push_back(E);
+
+		// Local file header
+		AppendU32(0x04034b50);			   // signature
+		AppendU16(20);					   // version needed
+		AppendU16(0);					   // flags
+		AppendU16(Method);				   // compression method
+		AppendU16(0);					   // last mod time
+		AppendU16(0);					   // last mod date
+		AppendU32(0);					   // crc32 (not validated by ZipFs)
+		AppendU32(E.CompressedSize);	   // compressed size
+		AppendU32(E.UncompressedSize);	   // uncompressed size
+		AppendU16((uint16_t)Name.size());  // file name length
+		AppendU16(0);					   // extra field length
+		Append(Name.data(), Name.size());  // file name
+		Append(FileData.data(), FileData.size());
+	}
+
+	zen::IoBuffer Build()
+	{
+		uint32_t CdOffset = (uint32_t)Data.size();
+
+		for (const Entry& E : Entries)
+		{
+			// Central directory record
+			AppendU32(0x02014b50);				 // signature
+			AppendU16(20);						 // version made by
+			AppendU16(20);						 // version needed
+			AppendU16(0);						 // flags
+			AppendU16(E.CompressionMethod);		 // compression method
+			AppendU16(0);						 // last mod time
+			AppendU16(0);						 // last mod date
+			AppendU32(0);						 // crc32
+			AppendU32(E.CompressedSize);		 // compressed size
+			AppendU32(E.UncompressedSize);		 // uncompressed size
+			AppendU16((uint16_t)E.Name.size());	 // file name length
+			AppendU16(0);						 // extra field length
+			AppendU16(0);						 // comment length
+			AppendU16(0);						 // disk index
+			AppendU16(0);						 // internal file attr
+			AppendU32(0);						 // external file attr
+			AppendU32(E.LocalHeaderOffset);		 // offset
+			Append(E.Name.data(), E.Name.size());
+		}
+
+		uint32_t CdSize = (uint32_t)Data.size() - CdOffset;
+
+		// End of central directory record
+		AppendU32(0x06054b50);				  // signature
+		AppendU16(0);						  // this disk
+		AppendU16(0);						  // cd start disk
+		AppendU16((uint16_t)Entries.size());  // cd records this disk
+		AppendU16((uint16_t)Entries.size());  // cd records total
+		AppendU32(CdSize);					  // cd size
+		AppendU32(CdOffset);				  // cd offset
+		AppendU16(0);						  // comment length
+
+		zen::IoBuffer Buffer(Data.size());
+		std::memcpy(Buffer.GetMutableView().GetData(), Data.data(), Data.size());
+		return Buffer;
+	}
+};
+
+}  // namespace
+
+TEST_CASE("zipfs.stored")
+{
+	const char* Content = "Hello, World!";
+
+	ZipBuilder Zip;
+	Zip.AddFile("test.txt", Content, std::strlen(Content), false);
+
+	zen::ZipFs Fs(Zip.Build());
+
+	zen::IoBuffer Result = Fs.GetFile("test.txt");
+	REQUIRE(Result);
+	CHECK(Result.GetView().GetSize() == std::strlen(Content));
+	CHECK(std::memcmp(Result.GetView().GetData(), Content, std::strlen(Content)) == 0);
+}
+
+TEST_CASE("zipfs.deflate")
+{
+	const char* Content = "This is some content that will be deflate compressed in the zip file.";
+
+	ZipBuilder Zip;
+	Zip.AddFile("compressed.txt", Content, std::strlen(Content), true);
+
+	zen::ZipFs Fs(Zip.Build());
+
+	zen::IoBuffer Result = Fs.GetFile("compressed.txt");
+	REQUIRE(Result);
+	CHECK(Result.GetView().GetSize() == std::strlen(Content));
+	CHECK(std::memcmp(Result.GetView().GetData(), Content, std::strlen(Content)) == 0);
+}
+
+TEST_CASE("zipfs.mixed")
+{
+	const char* StoredContent  = "stored content";
+	const char* DeflateContent = "deflate content that is compressed";
+
+	ZipBuilder Zip;
+	Zip.AddFile("stored.txt", StoredContent, std::strlen(StoredContent), false);
+	Zip.AddFile("deflated.txt", DeflateContent, std::strlen(DeflateContent), true);
+
+	zen::ZipFs Fs(Zip.Build());
+
+	zen::IoBuffer Stored = Fs.GetFile("stored.txt");
+	REQUIRE(Stored);
+	CHECK(Stored.GetView().GetSize() == std::strlen(StoredContent));
+	CHECK(std::memcmp(Stored.GetView().GetData(), StoredContent, std::strlen(StoredContent)) == 0);
+
+	zen::IoBuffer Deflated = Fs.GetFile("deflated.txt");
+	REQUIRE(Deflated);
+	CHECK(Deflated.GetView().GetSize() == std::strlen(DeflateContent));
+	CHECK(std::memcmp(Deflated.GetView().GetData(), DeflateContent, std::strlen(DeflateContent)) == 0);
+}
+
+TEST_CASE("zipfs.not_found")
+{
+	const char* Content = "data";
+
+	ZipBuilder Zip;
+	Zip.AddFile("exists.txt", Content, std::strlen(Content), false);
+
+	zen::ZipFs Fs(Zip.Build());
+
+	zen::IoBuffer Result = Fs.GetFile("missing.txt");
+	CHECK(!Result);
+}
+
+TEST_SUITE_END();
+
+#endif	// ZEN_WITH_TESTS