Expose image studio flow and related admin controls

Bundle the current backend and web changes into one publishable snapshot
from the server worktree so the remote mirror reflects the deployed source.

Constraint: Push the existing mixed worktree from /docker/new-api/src without reshaping files
Rejected: Split into feature-specific commits | current worktree is already a single undifferentiated snapshot
Confidence: medium
Scope-risk: moderate
Directive: Split future feature work before deployment to preserve clearer history
Tested: git status inspection; git diff --stat review
Not-tested: build, lint, unit tests, integration tests

relay/helper/valid_request.go

@@ -143,11 +143,11 @@ func GetAndValidOpenAIImageRequest(c *gin.Context, relayMode int) (*dto.ImageReq
 	imageRequest := &dto.ImageRequest{}
 
 	switch relayMode {
-	case relayconstant.RelayModeImagesEdits:
+	case relayconstant.RelayModeImagesEdits, relayconstant.RelayModeImagesGenerations:
 		if strings.Contains(c.Request.Header.Get("Content-Type"), "multipart/form-data") {
 			_, err := c.MultipartForm()
 			if err != nil {
-				return nil, fmt.Errorf("failed to parse image edit form request: %w", err)
+				return nil, fmt.Errorf("failed to parse image form request: %w", err)
 			}
 			formData := c.Request.PostForm
 			imageRequest.Prompt = formData.Get("prompt")