New download mode alongside Soulseek, YouTube, Tidal, and Qobuz. Uses
community-run REST API instances (no auth required) that serve Tidal CDN
FLAC streams. Features quality fallback chain (hires→lossless→high→low),
automatic instance rotation on failure, and full hybrid mode support.
Also fixes 6 missing streaming source checks for HiFi and Qobuz in the
frontend that were blocking playback with "format not supported" errors.
