feat(dashboard): embedded FastAPI backend with REST API + WebSocket

- FastAPI runs in MeshAI asyncio loop (no separate process)
- REST API: /api/status, /api/health, /api/nodes, /api/edges,
  /api/regions, /api/sources, /api/config, /api/alerts
- WebSocket at /ws/live pushes health updates and alerts
- Config CRUD: GET/PUT per section with validation and save
- DashboardConfig with port/host in config.yaml

pyproject.toml

@@ -36,6 +36,8 @@ dependencies = [
     "google-genai>=1.0.0",
     "rich>=13.0.0",
     "httpx>=0.25.0",
+    "fastapi>=0.110.0",
+    "uvicorn[standard]>=0.27.0",
 ]
 
 [project.optional-dependencies]