Version:
- New app/__version__.py with 'dev' fallback for local dev
- Dockerfile injects APP_VERSION build arg from CI tag
- Health endpoint and footer now show actual release version
- Test updated to accept 'dev' in non-Docker environments
File size:
- Capture filesize/filesize_approx from yt-dlp extract_info
- Write to DB via update_job_progress and broadcast via SSE
- New 'Size' column in download table (hidden on mobile)
- formatSize helper: bytes → human-readable (KB/MB/GB)
- Frontend store picks up filesize from SSE events
