perf: 提升后端高并发承载能力

backend/internal/api/middleware.go

@@ -89,8 +89,8 @@ func authenticateRequest(c *gin.Context) (*model.User, error) {
 		return nil, errInvalidToken
 	}
 
-	var user model.User
-	if err := db.DB.First(&user, uint(userID)).Error; err != nil {
+	user, err := db.LoadUserByID(uint(userID))
+	if err != nil {
 		return nil, errUserNotFound
 	}