- New ignore_db module with SQLite-backed dismissal storage
- Groups flagged as not-a-dupe are persisted to ~/.config/deduper/ignores.db
- Fingerprint based on sorted SHA256 hashes (content-stable)
- Ignored groups filtered out on subsequent runs
- Review UI: green "Not a dupe" button per group
- Dismissed groups fade out immediately in browser
- DEDUPER_DB_DIR env var to override DB location
- 4 new unit tests for ignore_db
- 29 tests passing
