Root cause of Sokhi's endless 0-findings: the SCAN resolved each track's path
through the path-mapping layer with NO fallback, while the APPLY
(_fix_missing_cover_art) uses `_resolve_file_path(...) or p` — i.e. it falls
back to the raw DB path when mapping returns nothing. On his Docker setup the
mapping returns None, so the scan set has_local=False and skipped every album
(never looking at the folder), even though the apply WOULD have written the
cover.jpg from the raw path.
Fix: make the scan match the apply — if mapping returns nothing but the raw DB
path is a real file (container path == stored path), use it as-is. Now the scan
actually inspects the folder, sees the missing cover.jpg, and flags it; the
apply then writes it from the embedded art.
Tests: unresolved-path-but-real-file → flagged (sidecar_from_embedded); the
fallback does NOT fire for a non-existent path (media-server-only stays skipped).
Kept the [cover-diag] logging from the prior commit to confirm on Sokhi's run.
2f3ade8acb