Dashboard overhaul, compute integration (#814)

- **Frontend dashboard overhaul**: Unified compute/main dashboards into a single shared UI. Added new pages for cache, projects, metrics, sessions, info (build/runtime config, system stats). Added live-update via WebSockets with pause control, sortable detail tables, themed styling. Refactored compute/hub/orchestrator pages into modular JS.
- **HTTP server fixes and stats**: Fixed http.sys local-only fallback when default port is in use, implemented root endpoint redirect for http.sys, fixed Linux/Mac port reuse. Added /stats endpoint exposing HTTP server metrics (bytes transferred, request rates). Added WebSocket stats tracking.
- **OTEL/diagnostics hardening**: Improved OTLP HTTP exporter with better error handling and resilience. Extended diagnostics services configuration.
- **Session management**: Added new sessions service with HTTP endpoints for registering, updating, querying, and removing sessions. Includes session log file support. This is still WIP.
- **CLI subcommand support**: Added support for commands with subcommands in the zen CLI tool, with improved command dispatch.
- **Misc**: Exposed CPU usage/hostname to frontend, fixed JS compact binary float32/float64 decoding, limited projects displayed on front page to 25 sorted by last access, added vscode:// link support.

Also contains some fixes from TSAN analysis.

1 files changed, 55 insertions, 0 deletions

diff --git a/src/zenserver/sessions/httpsessions.h b/src/zenserver/sessions/httpsessions.h
new file mode 100644
index 000000000..e07f3b59b
--- /dev/null
+++ b/src/zenserver/sessions/httpsessions.h
@@ -0,0 +1,55 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+#include <zenhttp/httpserver.h>
+#include <zenhttp/httpstats.h>
+#include <zenhttp/httpstatus.h>
+#include <zentelemetry/stats.h>
+
+namespace zen {
+
+class SessionsService;
+
+class HttpSessionsService final : public HttpService, public IHttpStatusProvider, public IHttpStatsProvider
+{
+public:
+	HttpSessionsService(HttpStatusService& StatusService, HttpStatsService& StatsService, SessionsService& Sessions);
+	virtual ~HttpSessionsService();
+
+	virtual const char* BaseUri() const override;
+	virtual void		HandleRequest(HttpServerRequest& Request) override;
+
+	virtual CbObject CollectStats() override;
+	virtual void	 HandleStatsRequest(HttpServerRequest& Request) override;
+	virtual void	 HandleStatusRequest(HttpServerRequest& Request) override;
+
+private:
+	struct SessionsStats
+	{
+		std::atomic_uint64_t SessionReadCount{};
+		std::atomic_uint64_t SessionWriteCount{};
+		std::atomic_uint64_t SessionDeleteCount{};
+		std::atomic_uint64_t SessionListCount{};
+		std::atomic_uint64_t RequestCount{};
+		std::atomic_uint64_t BadRequestCount{};
+	};
+
+	inline LoggerRef Log() { return m_Log; }
+
+	LoggerRef m_Log;
+
+	void Initialize();
+
+	void ListSessionsRequest(HttpRouterRequest& Req);
+	void SessionRequest(HttpRouterRequest& Req);
+
+	HttpStatusService&		 m_StatusService;
+	HttpStatsService&		 m_StatsService;
+	HttpRequestRouter		 m_Router;
+	SessionsService&		 m_Sessions;
+	SessionsStats			 m_SessionsStats;
+	metrics::OperationTiming m_HttpRequests;
+};
+
+}  // namespace zen