Improves the time offset feature by making manual offsets persistent and enhancing the user workflow.
- **Persistent Manual Offsets**: Manual offsets are now saved to IndexedDB, keyed by filename. They are automatically applied when the same file is loaded in a future session.
- **Click to Revert & Forget**: The "Manual" status indicator is now clickable. Clicking it reverts to the auto-calculated offset and, crucially, deletes the saved manual offset from the database. This ensures future sessions will correctly default to the automatic calculation.
- **Consistent UI**: The "Manual" indicator now appears instantly with a consistent gray style, whether set manually or loaded from cache, removing UI ambiguity.
- **Refactored Sync Logic**: The `revertToAutoOffset` function has been refactored to reuse the core `forceResyncWithOffset` logic. This reduces code duplication and centralizes the synchronization process, making it more robust and easier to maintain.