feat: Add option to skip already processed items in library processing
- Add "Skip items already processed by Aphrodite" checkbox to LibraryForm
- Implement --skip-processed command line argument in aphrodite.py
- Add skipProcessed parameter throughout the workflow chain (frontend → API → workflow manager → script)
- Filter out items with aphrodite-overlay metadata tag when skip option is enabled
- Display count of skipped vs remaining items for user feedback
- Uses configurable tag name from settings.yaml metadata_tagging section
This feature allows users to efficiently re-run library processing without
wasting time on items that have already been successfully processed by Aphrodite.