refactor: complete rewrite as React+FastAPI dashboard

Replace monolithic Jinja2 template with modern stack:

Backend (FastAPI):
- Modular router/service architecture
- Async PostgreSQL (asyncpg) for news from n8n pipeline
- Live Unraid server stats (2 servers via API)
- Home Assistant, Vikunja tasks, weather (wttr.in)
- WebSocket broadcast for real-time updates (15s)
- TTL cache per endpoint, all config via ENV vars

Frontend (React + Vite + TypeScript):
- Glassmorphism dark theme with Tailwind CSS
- Responsive grid: mobile/tablet/desktop/ultrawide
- Weather cards, hourly forecast, news with category tabs
- Server stats (CPU ring, RAM bar, Docker list)
- Home Assistant controls, task management
- Live clock, WebSocket connection indicator

Infrastructure:
- Multi-stage Dockerfile (node:22-alpine + python:3.11-slim)
- docker-compose with full ENV configuration
- Kaniko CI/CD pipeline for GitLab registry

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

server/cache.py

@@ -0,0 +1,41 @@
+"""Simple async-safe TTL cache."""
+
+from __future__ import annotations
+
+import asyncio
+import time
+from typing import Any, Dict, Optional, Tuple
+
+
+class TTLCache:
+    """Thread/async-safe in-memory cache with per-key TTL."""
+
+    def __init__(self) -> None:
+        self._store: Dict[str, Tuple[Any, float]] = {}
+        self._lock = asyncio.Lock()
+
+    async def get(self, key: str) -> Optional[Any]:
+        async with self._lock:
+            entry = self._store.get(key)
+            if entry is None:
+                return None
+            value, expires_at = entry
+            if time.time() > expires_at:
+                del self._store[key]
+                return None
+            return value
+
+    async def set(self, key: str, value: Any, ttl: int) -> None:
+        async with self._lock:
+            self._store[key] = (value, time.time() + ttl)
+
+    async def invalidate(self, key: str) -> None:
+        async with self._lock:
+            self._store.pop(key, None)
+
+    async def clear(self) -> None:
+        async with self._lock:
+            self._store.clear()
+
+
+cache = TTLCache()