New download_source column on library_history table records which source
(Soulseek, Tidal, Qobuz, HiFi, YouTube, Deezer) each track was downloaded
from. Extracted from context username during post-processing.
Frontend shows source badge alongside quality badge on each download entry.
Source breakdown bar below tabs shows per-source totals with color-coded
chips (e.g., "Soulseek: 847 | Tidal: 203"). Includes DB migration for
existing installs. Existing entries show quality only (source is NULL).
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