fix(backend): 修复视频生成接口401认证失败问题

- 修正可灵视频任务提交时认证失败导致的视频生成错误
- 解决接口返回500错误的问题
- 优化视频生成相关的错误日志提示
- 保证上传目录准备状态的正确显示
- 提升后台服务日志的稳定性和连续性

backend/app/schemas/design.py

@@ -27,8 +27,9 @@ class DesignCreate(BaseModel):
     """创建设计请求"""
     category_id: int = Field(..., description="品类ID")
     sub_type_id: Optional[int] = Field(None, description="子类型ID")
+    sub_type_name: Optional[str] = Field(None, max_length=50, description="自定义子类型名称")
     color_id: Optional[int] = Field(None, description="颜色ID")
-    prompt: str = Field(..., min_length=1, max_length=2000, description="设计需求")
+    prompt: Optional[str] = Field(None, max_length=2000, description="设计需求")
     carving_technique: Optional[str] = Field(None, max_length=50, description="雕刻工艺")
     design_style: Optional[str] = Field(None, max_length=50, description="设计风格")
     motif: Optional[str] = Field(None, max_length=100, description="题材纹样")