Remove the per-source download-quality dropdowns (Tidal/HiFi/Qobuz/Deezer/
Amazon) — with the global ranked-targets system they were redundant and
conflicting. Add quality_tier_for_source(): picks the LOWEST source tier
that satisfies the user's top target (respects the quality ceiling, saves
bandwidth) or the source's max as best effort. Every source's search +
download + retry path now derives its tier from the global profile instead
of config_manager.get('<source>_download.quality').
Settings keep the per-source allow_fallback toggles; the quality selects are
replaced with a note pointing at Quality Profile.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
