core/maintenance/dedupe_source_ids.py + scripts/dedupe_source_ids.py: find
source-id clusters held by differently-named artists (the enrichment-corruption
signature) and clear the id + match-status on those rows so the now-name-checked
workers re-derive each correctly on the next enrichment pass. Same-name
duplicates (one artist across two media servers) are left untouched.
Dry-run by default; --apply to write. 8 seam tests cover detection (corrupt vs
legit), dry-run safety, apply behaviour, and the no-op case.
