Apply migrations and backfill scripts for location data and approval flow, including:
- Implemented backfill_park_locations function to populate missing park locations from approved submissions
- Adjusted process_approval_transaction to properly handle location creation and linking
- Added admin-triggered backfill trigger point and related migration scaffolding for execution
- Created edge-function and admin UI hook to run backfill as needed
- Ensure search_path and relational data usage fixes for stability
