Fixes: 1) Validate gateway presence in `process_transaction_changes` signal; 2) Add missing imports for `Type`, `create_object`, and `AbstractGateway`;
Extra: 1) Cleanup unused diff lines in migrations files; 2) Improve JSONField, FloatField, and PositiveIntegerField declarations by consolidating into single lines; 3) Remove redundant match-case logic in `signals.py`.
Fixes: 1) Correct import order in `payments.admin`.
Extra: 1) Update `productimage.priority` field in `core` app with default value and help text; 2) Include `integration_path` in `Vendor` admin additional fields.