178a43dd5d
- Add migration for UNIQUE index on external_ref column (bd-897a) - Add validation for duplicate external_ref in batch imports (bd-7315) - Add query planner test to verify index usage (bd-f9a1) - Add concurrent import tests for external_ref (bd-3f6a) The migration detects existing duplicates and fails gracefully. Batch imports now reject duplicates with clear error messages. Tests verify the index is actually used by SQLite query planner. Amp-Thread-ID: https://ampcode.com/threads/T-45ca66ed-3912-46c4-963c-caa7724a9a2f Co-authored-by: Amp <amp@ampcode.com>