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/attachment.py

@@ -1,14 +1,17 @@
 import uuid
 from datetime import datetime
 
-from pydantic import BaseModel, ConfigDict
+from pydantic import BaseModel, ConfigDict, Field
+
+from app.schemas.user import UserDisplay
 
 
 class AttachmentRead(BaseModel):
     id: uuid.UUID
     filename: str
-    file_size: int
-    uploaded_by: uuid.UUID
+    file_size: int = Field(alias="size")
+    uploaded_by: UserDisplay | None = None
+    uploaded_by_id: uuid.UUID | None = None
     uploaded_at: datetime
 
-    model_config = ConfigDict(from_attributes=True)
+    model_config = ConfigDict(from_attributes=True, populate_by_name=True)