MQTT-based live CPU/RAM metrics + remove auth from HA control

- Enrich server data with MQTT system topics (cpu_usage_percent,
  ram_usage_percent, temp, model etc.) published by Unraid MQTT Agent
- Works for both Daddelolymp and Adriahub topics
- MQTT overlay runs on every request (even cached) for fresh metrics
- Remove JWT auth from /api/ha/control — local dashboard doesn't need it
- Add cpu brand field to GraphQL query

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/routers/homeassistant.py

@@ -5,10 +5,9 @@ from __future__ import annotations
 import logging
 from typing import Any, Dict, Optional
 
-from fastapi import APIRouter, Depends
+from fastapi import APIRouter
 from pydantic import BaseModel
 
-from server.auth import require_admin
 from server.cache import cache
 from server.config import get_settings
 from server.services.ha_service import call_ha_service, fetch_ha_data
@@ -58,7 +57,6 @@ class HAControlRequest(BaseModel):
 @router.post("/ha/control")
 async def control_ha(
     body: HAControlRequest,
-    admin_user: str = Depends(require_admin),  # noqa: ARG001
 ) -> Dict[str, Any]:
     """Control a Home Assistant entity (toggle light, open cover, etc.)."""