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/s3.go

@@ -47,14 +47,14 @@ func NewS3Controller(_log *zap.Logger, _us services.S3Service) Controller {
 			{
 				HttpMethod:   GET,
 				Path:         "/avatar",
-				Authorization: enums.UserRole,
+				Authorization: enums.GuestRole,
 				Middleware:   []gin.HandlerFunc{},
 				Function:     ctrl.getAvatarUploadUrl,
 			},
 			{
 				HttpMethod:   GET,
 				Path:         "/image",
-				Authorization: enums.UserRole,
+				Authorization: enums.GuestRole,
 				Middleware:   []gin.HandlerFunc{},
 				Function:     ctrl.getImageUploadUrl,
 			},
@@ -62,14 +62,11 @@ func NewS3Controller(_log *zap.Logger, _us services.S3Service) Controller {
 	}
 }
 
-// XXX: untested
 //	@Summary Get presigned URL for avatar upload
 //	@Tags Upload
 //	@Accept		json
 //	@Produce	json
-//	@Security	JWT
 //	@Success	200		{object}	models.PresignedUploadResponse	"Presigned URL and form data"
-//	@Failure	500		"Internal server error"
 //	@Router		/upload/avatar [get]
 func (ctrl *S3Controller) getAvatarUploadUrl(c *gin.Context) {
 	url, formData, err := ctrl.s3.CreateAvatarUrl()
@@ -85,14 +82,11 @@ func (ctrl *S3Controller) getAvatarUploadUrl(c *gin.Context) {
 	})
 }
 
-// XXX: untested
 //	@Summary Get presigned URL for image upload
 //	@Tags Upload
 //	@Accept		json
 //	@Produce	json
-//	@Security	JWT
 //	@Success	200		{object}	models.PresignedUploadResponse	"Presigned URL and form data"
-//	@Failure	500		"Internal server error"
 //	@Router		/upload/image [get]
 func (ctrl *S3Controller) getImageUploadUrl(c *gin.Context) {
 	url, formData, err := ctrl.s3.CreateImageUrl()