Three related fixes to Tidal track matching and downloading:
1. version-field handling — Tidal stores remix/live/edit qualifiers in a
dedicated `track.version` attribute (e.g. name="Emerge",
version="Junkie XL Remix"), not in the track name. The qualifier
filter and the matcher only looked at name/album, so the exact
recording was discarded. Fold `version` into both the qualifier
haystack and the candidate title passed to MusicMatchingEngine.
2. divergent-version penalty — once versions are visible, OTHER cuts of
the same base become candidates ("(Shazam Remix)" vs "(southstar
Remix)"). Neither title is a prefix of the other, so the prefix-based
version check missed them and the raw ratio stayed high off the
shared base. Apply a heavy penalty when both titles carry different
version descriptors so the wrong cut can't outscore the threshold.
3. rate-limit backoff — the trackManifests endpoint is aggressively
rate-limited; a bare request failed 429 instantly, burned the quality
tier, re-queued the track and hammered again (a self-amplifying
storm). Honour Retry-After / exponential backoff with a bounded retry
count and shutdown-aware sleep.
Adds unit + end-to-end tests for all three.
