Impact Executive Dashboard v15 - API Sync reliability update

1. Replace the application files with this package.
2. Open sync_settings.php. The application will add the new settings columns automatically if the DB user can ALTER tables.
3. If you see an ALTER/column permission error, run upgrade_sync_v15.sql once in phpMyAdmin.
4. Regenerate/revoke the Bearer token previously exposed in Diagnostic IDs 1/2, then save the new token in Sync Settings.
5. Test Payments with the exact same one-day range that succeeds in Postman.
6. Test Claims with a one-day range.
7. Keep API Batch Size at 1 day initially.
8. Set Automatic Rolling Window to 24 hours (or 48/72 if late-posted records are common).
9. Run Manual / Backfill Sync for historical ranges. It will split them into daily batches.
10. Keep cron running every minute; the application enforces the configured 10-minute interval.

Security: v15 masks Bearer tokens in all diagnostic outputs, including curl_info.request_header and verbose logs.