- Fix backup.py PRESERVED_FIELDS column names (lat/lng -> latitude/longitude)
to match actual DB schema (pre-existing bug)
- Add backup_gps() and restore_gps() dedicated GPS-only functions
- Add /api/gps/backup and /api/gps/restore API endpoints
- Add /api/gps/restore/upload for restoring from uploaded backup files
- Add /api/db/wipe endpoint to clear all asset records
- Update UI with GPS-only Backup button, Restore GPS from File picker,
and Wipe All Assets with double-confirmation dialog
- Fix backup listing to scan both seed-data/ and project root