feat(web-console): cherry-pick React web console GUI from gary-the-ai fork

Cherry-pick the Hermes Web Console from gary-the-ai/hermes-web-console-gui.
React + TypeScript frontend with Vite, Python aiohttp backend API.

Components:
- web_console/ — React frontend (chat, sessions, memory, settings, skills,
  gateway config, cron, workspace, tools, browser, insights pages)
- gateway/web_console/ — Python backend API (23 endpoints, SSE event bus,
  11 service modules)
- gateway/platforms/api_server_ui.py — embedded browser UI for API server
- gateway/platforms/api_server.py — route registration refactored into
  _register_routes(), web console mounted via maybe_register_web_console()
- run-gui.sh / setup-gui.sh — one-command launch and setup scripts
- tests/gateway/test_api_server_gui_mount.py — 4 integration tests (passing)
- tests/web_console/ — 13 backend test files (51 passing)
- docs/plans/ — implementation plan, API schema, frontend architecture

Fix: added missing ModelContextError class and CRON_MIN_CONTEXT_TOKENS to
cron/scheduler.py (pre-existing import bug).

Closes #325

gateway/web_console/api/usage.py

@@ -0,0 +1,53 @@
+import logging
+from aiohttp import web
+
+logger = logging.getLogger("usage_api")
+
+async def handle_get_usage_insights(request: web.Request) -> web.Response:
+    try:
+        days = int(request.query.get("days", 30))
+        source = request.query.get("source")
+        
+        from hermes_state import SessionDB
+        from agent.insights import InsightsEngine
+        
+        db = SessionDB()
+        engine = InsightsEngine(db)
+        report = engine.generate(days=days, source=source)
+        db.close()
+        
+        return web.json_response({"ok": True, "report": report})
+    except Exception as e:
+        logger.error(f"Failed to fetch usage insights: {e}")
+        return web.json_response({"ok": False, "error": str(e)}, status=500)
+
+async def handle_get_session_usage(request: web.Request) -> web.Response:
+    try:
+        session_id = request.match_info.get("id")
+        if not session_id:
+            return web.json_response({"ok": False, "error": "Session ID required"}, status=400)
+            
+        from hermes_state import SessionDB
+        db = SessionDB()
+        try:
+            session = db.get_session(session_id)
+            if not session:
+                return web.json_response({"ok": False, "error": "Not found"}, status=404)
+                
+            return web.json_response({"ok": True, "session_usage": {
+                "input_tokens": getattr(session, "input_tokens", 0) or 0,
+                "output_tokens": getattr(session, "output_tokens", 0) or 0,
+                "cache_read_tokens": getattr(session, "cache_read_tokens", 0) or 0,
+                "cache_write_tokens": getattr(session, "cache_write_tokens", 0) or 0,
+                "total_tokens": getattr(session, "total_tokens", 0) or 0,
+                "estimated_cost_usd": getattr(session, "estimated_cost_usd", 0.0) or 0.0,
+            }})
+        finally:
+            db.close()
+    except Exception as e:
+        logger.error(f"Failed to fetch session usage: {e}")
+        return web.json_response({"ok": False, "error": str(e)}, status=500)
+
+def register_usage_api_routes(app: web.Application) -> None:
+    app.router.add_get("/api/gui/usage/insights", handle_get_usage_insights)
+    app.router.add_get("/api/gui/usage/session/{id}", handle_get_session_usage)