style: fix gofmt and ineffassign lint errors

- gofmt: realign AffiliateDetail struct tags in affiliate_service.go
- ineffassign: remove dead seenCompleted assignment before return in account_test_service.go

backend/internal/service/account_test_service.go

@@ -1188,7 +1188,6 @@ func (s *AccountTestService) processOpenAIStream(c *gin.Context, body io.Reader)
 				s.sendEvent(c, TestEvent{Type: "content", Text: delta})
 			}
 		case "response.completed", "response.done":
-			seenCompleted = true
 			s.sendEvent(c, TestEvent{Type: "test_complete", Success: true})
 			return nil
 		case "response.failed":