Each streaming source (Tidal, Qobuz, HiFi, Deezer) now has an "Allow
quality fallback" checkbox in Settings. When disabled, the source only
tries the exact quality selected — if unavailable, it skips and lets
the orchestrator try the next source. Default is ON (current behavior).
Adds Tidal as a third download source alongside Soulseek and YouTube. Uses the tidalapi library with device-flow authentication to search and download tracks in configurable quality (Low/High/Lossless/HiRes) with automatic fallback. Integrates into the download orchestrator for all modes (Tidal Only, Hybrid with fallback chain), the transfer monitor, post-processing pipeline, and file finder. Frontend includes download settings with quality selector, device auth flow, and dynamic sidebar/dashboard labels that reflect the active download source. No breaking changes for existing users.
