- Add ScanWarning struct with FilePath/Phase/Err to ScanMetrics - Add mutex-protected addWarning method for concurrent use - Reclassify walk, extraction, commit, orphan, variant, FTS failures as warnings - Update commitBatch to return only fatal tx.Commit errors - Update cachedLinkArtist to check errors via database.IsUniqueViolation - Update handleConfigUpdate to capture and log scan warning count