Add MP4 scan progress visibility in UI

- Add broadcast_scan_started, broadcast_scan_progress, broadcast_scan_completed to WebSocketService
- Inject WebSocketService into AnimeService for real-time scan progress broadcasts
- Add CSS styles for scan progress overlay with spinner, stats, and completion state
- Update app.js to handle scan events and display progress overlay
- Add unit tests for new WebSocket broadcast methods
- All 1022 tests passing

data/config_backups/config_backup_20251223_182300.json

@@ -0,0 +1,24 @@
+{
+  "name": "Aniworld",
+  "data_dir": "data",
+  "scheduler": {
+    "enabled": true,
+    "interval_minutes": 60
+  },
+  "logging": {
+    "level": "INFO",
+    "file": null,
+    "max_bytes": null,
+    "backup_count": 3
+  },
+  "backup": {
+    "enabled": false,
+    "path": "data/backups",
+    "keep_days": 30
+  },
+  "other": {
+    "master_password_hash": "$pbkdf2-sha256$29000$RYgRIoQwBuC8N.bcO0eoNQ$6Cdc9sZvqy8li/43B0NcXYlysYrj/lIqy2E7gBtN4dk",
+    "anime_directory": "/mnt/server/serien/Serien/"
+  },
+  "version": "1.0.0"
+}