refactor: Fix linter errors by auto-apply

- Apply automated linter fixes
- Manually reformat fields in model/service.go
- Resolve code complexity issues

router/controller/auth/plain.go

@@ -26,6 +26,7 @@ func (c *PlainAuthController) Handler() gin.HandlerFunc {
 				Send(ginCtx)
 			if sendErr != nil {
 				ginCtx.Writer.WriteHeader(http.StatusInternalServerError)
+
 				return
 			}
 
@@ -41,6 +42,7 @@ func (c *PlainAuthController) Handler() gin.HandlerFunc {
 				Send(ginCtx)
 			if sendErr != nil {
 				ginCtx.Writer.WriteHeader(http.StatusInternalServerError)
+
 				return
 			}