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, 89 insertions, 1 deletions

diff --git a/src/zencore/system.cpp b/src/zencore/system.cpp
index 23178814c..6909e1a9b 100644
--- a/src/zencore/system.cpp
+++ b/src/zencore/system.cpp
@@ -14,20 +14,27 @@
 #	include <zencore/windows.h>
 
 ZEN_THIRD_PARTY_INCLUDES_START
-#	include <iphlpapi.h>
 #	include <winsock2.h>
+#	include <ws2tcpip.h>
+#	include <iphlpapi.h>
 #	include <pdh.h>
 #	pragma comment(lib, "pdh.lib")
 ZEN_THIRD_PARTY_INCLUDES_END
 #elif ZEN_PLATFORM_LINUX
 #	include <sys/utsname.h>
 #	include <unistd.h>
+#	include <ifaddrs.h>
+#	include <arpa/inet.h>
+#	include <net/if.h>
 #elif ZEN_PLATFORM_MAC
 #	include <unistd.h>
 #	include <mach/mach.h>
 #	include <mach/mach_host.h>
 #	include <sys/types.h>
 #	include <sys/sysctl.h>
+#	include <ifaddrs.h>
+#	include <arpa/inet.h>
+#	include <net/if.h>
 #endif
 
 namespace zen {
@@ -140,6 +147,51 @@ GetSystemMetrics()
 
 	return Metrics;
 }
+
+std::vector<std::string>
+GetLocalIpAddresses()
+{
+	std::vector<std::string> Result;
+
+	ULONG BufSize	= 15000;
+	auto* Addresses = static_cast<IP_ADAPTER_ADDRESSES*>(Memory::Alloc(BufSize));
+
+	ULONG Flags = GAA_FLAG_SKIP_DNS_SERVER | GAA_FLAG_SKIP_MULTICAST | GAA_FLAG_SKIP_ANYCAST;
+	ULONG Ret	= GetAdaptersAddresses(AF_INET, Flags, nullptr, Addresses, &BufSize);
+	if (Ret == ERROR_BUFFER_OVERFLOW)
+	{
+		Memory::Free(Addresses);
+		Addresses = static_cast<IP_ADAPTER_ADDRESSES*>(Memory::Alloc(BufSize));
+		Ret		  = GetAdaptersAddresses(AF_INET, Flags, nullptr, Addresses, &BufSize);
+	}
+
+	if (Ret == NO_ERROR)
+	{
+		for (IP_ADAPTER_ADDRESSES* Adapter = Addresses; Adapter != nullptr; Adapter = Adapter->Next)
+		{
+			if (Adapter->OperStatus != IfOperStatusUp)
+			{
+				continue;
+			}
+			if (Adapter->IfType == IF_TYPE_SOFTWARE_LOOPBACK)
+			{
+				continue;
+			}
+			for (IP_ADAPTER_UNICAST_ADDRESS* Unicast = Adapter->FirstUnicastAddress; Unicast != nullptr; Unicast = Unicast->Next)
+			{
+				sockaddr_in* SockAddr = reinterpret_cast<sockaddr_in*>(Unicast->Address.lpSockaddr);
+				char		 AddrBuf[INET_ADDRSTRLEN];
+				if (inet_ntop(AF_INET, &SockAddr->sin_addr, AddrBuf, sizeof(AddrBuf)))
+				{
+					Result.emplace_back(AddrBuf);
+				}
+			}
+		}
+	}
+
+	Memory::Free(Addresses);
+	return Result;
+}
 #elif ZEN_PLATFORM_LINUX
 std::string
 GetMachineName()
@@ -350,6 +402,42 @@ GetSystemMetrics()
 #	error "Unknown platform"
 #endif
 
+#if ZEN_PLATFORM_LINUX || ZEN_PLATFORM_MAC
+std::vector<std::string>
+GetLocalIpAddresses()
+{
+	std::vector<std::string> Result;
+
+	ifaddrs* Interfaces = nullptr;
+	if (getifaddrs(&Interfaces) != 0)
+	{
+		return Result;
+	}
+
+	for (ifaddrs* Iface = Interfaces; Iface != nullptr; Iface = Iface->ifa_next)
+	{
+		if (Iface->ifa_addr == nullptr || Iface->ifa_addr->sa_family != AF_INET)
+		{
+			continue;
+		}
+		if ((Iface->ifa_flags & IFF_LOOPBACK) != 0 || (Iface->ifa_flags & IFF_UP) == 0)
+		{
+			continue;
+		}
+
+		sockaddr_in* SockAddr = reinterpret_cast<sockaddr_in*>(Iface->ifa_addr);
+		char		 AddrBuf[INET_ADDRSTRLEN];
+		if (inet_ntop(AF_INET, &SockAddr->sin_addr, AddrBuf, sizeof(AddrBuf)))
+		{
+			Result.emplace_back(AddrBuf);
+		}
+	}
+
+	freeifaddrs(Interfaces);
+	return Result;
+}
+#endif
+
 ExtendedSystemMetrics
 ApplyReportingOverrides(ExtendedSystemMetrics Metrics)
 {