Add ODF support, sample files, and docs

Revamp docs to recommend a two-stage content pipeline (Upload → Processing → Display), clarify supported formats, note LibreOffice requirement for conversions, and update config examples and wording/typos. Add ODF formats (.odp, .ods, .odt) to OfficeRenderer EXTENSIONS so those files are recognized. Include sample ODF/office files in rotation/ for testing. Update requirements.txt (add requests and pin pydantic-core==2.41.5). These changes enable network upload workflows and encourage processing to keep invalid files out of the live media directory.

Took 40 minutes

Implement playlist versioning and watcher thread

Introduces a versioned playlist with thread-safe updates and a background watcher for live rotation content changes. Updates API to return playlist version and items, refactors config for scan interval, and improves player.js to handle playlist updates and robust media advancement. Removes unused video extension, updates styles, and cleans up rotation demo files.

Took 1 hour 27 minutes