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, 83 insertions, 0 deletions

diff --git a/src/zenserver/sessions/sessions.h b/src/zenserver/sessions/sessions.h
new file mode 100644
index 000000000..db9704430
--- /dev/null
+++ b/src/zenserver/sessions/sessions.h
@@ -0,0 +1,83 @@
+// Copyright Epic Games, Inc. All Rights Reserved.
+
+#pragma once
+
+#include <zencore/compactbinary.h>
+#include <zencore/logbase.h>
+#include <zencore/thread.h>
+#include <zencore/uid.h>
+
+ZEN_THIRD_PARTY_INCLUDES_START
+#include <tsl/robin_map.h>
+ZEN_THIRD_PARTY_INCLUDES_END
+
+#include <optional>
+#include <string>
+#include <vector>
+
+namespace zen {
+
+class SessionLogStore;
+class SessionLog;
+
+/** Session tracker
+ *
+ * Acts as a log and session info concentrator when dealing with multiple
+ * servers and external processes acting as a group.
+ */
+
+class SessionsService
+{
+public:
+	struct SessionInfo
+	{
+		Oid			Id;
+		std::string AppName;
+		Oid			JobId;
+		CbObject	Metadata;
+		DateTime	CreatedAt;
+		DateTime	UpdatedAt;
+	};
+
+	class Session : public TRefCounted<Session>
+	{
+	public:
+		Session(const SessionInfo& Info);
+		~Session();
+
+		Session(Session&&) = delete;
+		Session& operator=(Session&&) = delete;
+
+		const SessionInfo& Info() const { return m_Info; }
+		void			   UpdateMetadata(CbObjectView Metadata)
+		{
+			// Should this be additive rather than replacing the whole thing? We'll see.
+			m_Info.Metadata	 = CbObject::Clone(Metadata);
+			m_Info.UpdatedAt = DateTime::Now();
+		}
+
+	private:
+		SessionInfo		m_Info;
+		Ref<SessionLog> m_Log;
+	};
+
+	SessionsService();
+	~SessionsService();
+
+	bool					  RegisterSession(const Oid& SessionId, std::string AppName, const Oid& JobId, CbObjectView Metadata);
+	bool					  UpdateSession(const Oid& SessionId, CbObjectView Metadata);
+	Ref<Session>			  GetSession(const Oid& SessionId) const;
+	std::vector<Ref<Session>> GetSessions() const;
+	bool					  RemoveSession(const Oid& SessionId);
+	uint64_t				  GetSessionCount() const;
+
+private:
+	LoggerRef& Log() { return m_Log; }
+
+	LoggerRef									   m_Log;
+	mutable RwLock								   m_Lock;
+	tsl::robin_map<Oid, Ref<Session>, Oid::Hasher> m_Sessions;
+	std::unique_ptr<SessionLogStore>			   m_SessionLogs;
+};
+
+}  // namespace zen