feat: remove authentication requirement for avatar and image upload endpoints;

fix: remove 500 error responses from upload endpoints;
fix: return validation error strings instead of error lists;
fix: handle invalid avatar upload IDs with 400 Bad Request response;
fix: add missing S3Controller to controller initialization;
fix: change avatar_upload_id to string type and update validation rules;
chore: add license header to smtp.go;
refactor: replace manual proxy implementation with httputil.ReverseProxy;
fix: inject S3Service dependency into ProfileService;
fix: set color and color_grad fields during profile update;
fix: correct DTO mapping for profile and settings;
fix: check object existence before copying in SaveUpload;
fix: adjust profile DTO mapping function for proper pointer handling

backend/internal/controllers/controller.go

@@ -28,7 +28,6 @@ import (
 	"path/filepath"
 
 	"github.com/gin-gonic/gin"
-	"github.com/go-playground/validator/v10"
 	"github.com/google/uuid"
 	"go.uber.org/zap"
 )
@@ -127,10 +126,9 @@ func GetRequest[ModelT any](c *gin.Context) (*dto.Request[ModelT], error) {
 	validate := validation.NewValidator()
 
 	if err := validate.Struct(body); err != nil {
-		errorList := err.(validator.ValidationErrors)
 		c.AbortWithStatusJSON(
 			http.StatusBadRequest,
-			gin.H{"error": errorList})
+			gin.H{"error": err.Error()})
 		return nil, err
 	}