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/services/s3.go

@@ -21,6 +21,7 @@ import (
 	"context"
 	"easywish/config"
 	minioclient "easywish/internal/minioClient"
+	errs "easywish/internal/errors"
 	"easywish/internal/utils"
 	"fmt"
 	"net/url"
@@ -126,8 +127,14 @@ func (s *s3ServiceImpl) SaveUpload(uploadID string, bucketAlias string) (*string
 	sourceBucket := minioclient.Buckets["uploads"]
 	bucket := minioclient.Buckets[bucketAlias]
 	newObjectKey := uuid.New().String()
-
-	_, err := s.minio.CopyObject(context.Background(), minio.CopyDestOptions{
+ 
+	_, err := s.minio.StatObject(context.Background(), sourceBucket, uploadID, minio.StatObjectOptions{})
+	if err != nil {
+		if minio.ToErrorResponse(err).Code == minio.NoSuchKey {
+			return nil, errs.ErrFileNotFound
+		}
+	}
+	_, err = s.minio.CopyObject(context.Background(), minio.CopyDestOptions{
 		Bucket: bucket,
 		Object: newObjectKey,
 	}, minio.CopySrcOptions{