- app.py: replace send_file with manual Range-aware chunked generator;
returns 206 on partial requests so browsers can seek/buffer properly.
Thumbnail route returns 202 while ffmpeg is generating.
- app_video.py: thumbnail generation moved to background gevent greenlet
(_generate_thumbnail_bg). get_thumbnail_path returns immediately with
RuntimeError('generating') if not cached; ffmpeg only ever runs once
per video (result cached in dash/thumbnails/).
- dash.html: replaced bottom card player with Bootstrap modal (modal-xl,
centered, dark bg) — video pops up in place regardless of scroll position.
- local-videos.js: rewritten to use Bootstrap modal; thumbnail loader
polls with fetch() and retries on 202 every 2s (up to 15x) instead of
setting img.src directly (which can't detect 202).
Co-authored-by: Copilot <[email protected]>
