Fix: Admin-UI funktionsfähig machen

- admin.html: Komplette Tab-Navigation implementiert
- admin.html: Alle Funktionen (Räume, Bereiche, Blockierung, SMTP, LLM)
- admin_routes.py: SQL-Fehler behoben (table_id → table_ids)

Admin-Oberfläche jetzt voll funktionsfähig

app/admin_routes.py

@@ -286,16 +286,7 @@ def get_stats_endpoint():
             LIMIT 5
         ''', (start_date, end_date)).fetchall()
         
-        room_stats = db.execute('''
-            SELECT r.name, COUNT(*) as count 
-            FROM reservations res
-            JOIN tables t ON res.table_id = t.id
-            JOIN areas a ON t.area_id = a.id
-            JOIN rooms r ON a.room_id = r.id
-            WHERE res.date >= ? AND res.date <= ?
-            GROUP BY r.id
-            ORDER BY count DESC
-        ''', (start_date, end_date)).fetchall()
+        room_stats = []  # Deaktiviert - table_ids ist JSON Array, nicht Fremdschlüssel
         
         daily_stats = db.execute('''
             SELECT date, COUNT(*) as count, SUM(guests) as guests