Remove 11 imports no longer needed after controller extractions: QMenu, QFileDialog, QScrollArea, QMessageBox, QColor, QObject, Property, dataclass, download_thumbnail, cache_size_bytes, evict_oldest, evict_oldest_thumbnails, MEDIA_EXTENSIONS, SearchState. main_window.py: 1140 -> 1128 lines (final Phase 1 state). behavior change: none