feat(ui): SoC Refactoring & Config Validation

- Theme Context ausgelagert (ThemeContext.tsx + useDarkMode.ts)
- Config Validation mit TMDB-API-Key Pflicht (config_validation.py)
- Cache Key Centralization (cache/keys.py)
- CD-Ripping mit abcde implementiert (Worker)
- Docker Compose mit Healthchecks & LOG_LEVEL
- ROADMAP.md & SAVEPOINT.md aktualisiert

docker/ui/src/pages/MetadataPreview.tsx

@@ -2,6 +2,7 @@ import { useState, useEffect } from 'react'
 import axios from 'axios'
 import { BookOpen, Music, Film, AlertCircle, CheckCircle, Search, Loader2 } from 'lucide-react'
 import type { LucideIcon } from 'lucide-react'
+import { useDarkMode } from '../context/ThemeContext'
 
 interface Metadata {
   type: 'movie' | 'tv' | 'music' | 'unknown'
@@ -38,6 +39,7 @@ export default function MetadataPreview() {
   const [loading, setLoading] = useState(false)
   const [error, setError] = useState<string | null>(null)
   const [confirming, setConfirming] = useState(false)
+  const { theme } = useDarkMode()
 
   const handleScan = async () => {
     if (!device) {