Embedded HTTP server with health endpoint

[sunba91-su]

Goal

Add a lightweight embedded HTTP server to the Go bot for health checks and future WebUI.

Acceptance Criteria

• Create internal/web/ package
• Start HTTP server alongside the Rocket.Chat client (in a goroutine)
• GET /health returns 200 with JSON body:

  {
    "status": "ok",
    "database": "connected",
    "rocketchat": "connected",
    "uptime": "1h23m45s"
  }

• Configurable via env vars:
  • WEBUI_ENABLED (default: true)
  • WEBUI_PORT (default: 8080)
• Graceful shutdown on SIGINT/SIGTERM
• Log when server starts/stops
• Server exits silently if WEBUI_ENABLED=false
• Update .env.example with new vars
• Update README env table

Technical Notes

• Use standard library net/http (no external router dependency)
• Use http.Server with ReadHeaderTimeout, WriteTimeout for basic hardening
• DB health: run a simple SELECT 1 via the store
• Rocket.Chat health: check if client is connected (add a IsConnected() bool method to Client if needed)
• Uptime: start a time.Time in main, pass to web handler via closure
• The /health endpoint should NOT require auth (it is for Docker HEALTHCHECK/load balancers)

Dependencies

• None (can be built independently)