修复前后端显示异常问题（受试者、中心、负责人、日期等）

backend/app/schemas/user.py

@@ -7,6 +7,14 @@ from pydantic import BaseModel, ConfigDict, Field
 UserRole = Literal["PM", "CRA", "PV", "IMP", "ADMIN"]
 
 
+class UserDisplay(BaseModel):
+  id: uuid.UUID
+  username: str
+  display_name: Optional[str] = None
+
+  model_config = ConfigDict(from_attributes=True)
+
+
 class UserBase(BaseModel):
     username: str = Field(min_length=1)
     role: UserRole