feat: add upload title fallback

backend/app/api/upload.py

@@ -59,6 +59,15 @@ def _user_designer_aliases(user: User) -> list[str]:
     return aliases
 
 
+def _generate_fallback_title(category: str, designer_name: str, unique_id: str) -> str:
+    category_name = str(category or "设计素材").strip() or "设计素材"
+    designer = str(designer_name or "").strip()
+    suffix = unique_id.replace("-", "")[:6]
+    if designer:
+        return f"{category_name}_{designer}_{suffix}"
+    return f"{category_name}_自动生成_{suffix}"
+
+
 def generate_thumbnail(image_path: str, thumb_path: str, size=(400, 400)):
     """生成缩略图 - 修复透明 PNG 问题"""
     with Image.open(image_path) as img:
@@ -115,7 +124,7 @@ def add_watermark(image_path: str, watermarked_path: str, watermark_text: str =
 @router.post("", summary="上传作品")
 async def upload_work(
     file: UploadFile = File(..., description="作品图片文件"),
-    title: str = Form(..., description="作品标题"),
+    title: Optional[str] = Form(None, description="作品标题"),
     description: Optional[str] = Form(None, description="作品描述"),
     category: str = Form(..., description="作品分类"),
     tags: Optional[str] = Form(None, description="标签，逗号分隔"),
@@ -191,10 +200,11 @@ async def upload_work(
         else:
             tags_str = None
         resolved_designer = str(designer_name or "").strip() or current_user.nickname or current_user.phone
+        resolved_title = str(title or "").strip() or _generate_fallback_title(category, resolved_designer, unique_id)
         
         # 创建数据库记录 - 修复所有字段问题
         work = Work(
-            title=title,
+            title=resolved_title,
             description=description or "",
             category=category,
             tags=tags_str,  # 修复：使用字符串而不是列表