- nib export: dump all entities to JSON (stdout or --output file)
- nib backup: atomic SQLite backup via VACUUM INTO (WAL-safe)
- Store.Backup() method on db layer
- Tests for both commands
- Cap list API limit at 200 to prevent unbounded queries
- Sanitize markdown output with DOMPurify to prevent XSS
- Add v4 migration with indexes on deleted_at and modified_at
- Fix v2 migration swallowed ALTER TABLE errors
- Tighten ~/.nib directory permissions to 0o700