- Model: rename `uk_model_name` -> `uk_model_name_delete_at`
(composite on `model_name` + `deleted_at`)
- Vendor: rename `uk_vendor_name` -> `uk_vendor_name_delete_at`
(composite on `name` + `deleted_at`)
- Keep legacy cleanup in `model/main.go` to drop old index names
(`uk_model_name`, `model_name`, `uk_vendor_name`, `name`) for compatibility.
Result: idempotent GORM migrations and no unnecessary index churn on MySQL restarts.
Files:
- `model/model_meta.go`
- `model/vendor_meta.go`
