Touch drags flip pages: the page follows the finger live, the axis locks
on first movement so vertical pans never flip, and edge drags get
rubber-band resistance. Swipes starting on interactive controls are
ignored. Swipe intent lives in bookSwipeDirection with unit tests.
- Introduced voiceover relationship to StoryBeats with AI-generated flag.
- Added BeatVoiceover component for playing audio narrations with a minimal interface.
- Updated StoryPage, StoryViewer, and StoryTableOfContents to display and handle voiceovers.
- Created Voiceovers collection for uploading and managing audio narrations for beats.
- Included migration script to support voiceover functionality in the database.
