YouTube restricts available formats for bot-like requests. Specifying
player_client=ios,web makes yt-dlp impersonate the iOS app which has
broader format access without requiring cookies.
--extract-audio + --audio-format mp3 handles conversion regardless of
source format, so the explicit --format bestaudio/best was unnecessarily
restrictive.
Cache-first was preventing updates from reaching users. Network-first
always fetches fresh content and only falls back to cache when offline.
Also bumps cache version to evict stale cache-first entries.
Adds a Settings panel to upload a cookies.txt file directly from the
browser, persisted in a named Docker volume. yt-dlp uses the file
when present to bypass YouTube bot detection.
