修复前后端显示异常问题（受试者、中心、负责人、日期等）

backend/app/api/v1/attachments.py

@@ -15,6 +15,7 @@ from app.crud import user as user_crud
 from app.crud import member as member_crud
 from app.core.security import decode_token
 from app.schemas.attachment import AttachmentRead
+from app.schemas.user import UserDisplay
 
 router = APIRouter()
 global_router = APIRouter()
@@ -74,7 +75,14 @@ async def upload_attachment(
         operator_id=current_user.id,
         operator_role=current_user.role,
     )
-    return attachment
+    return AttachmentRead(
+        id=attachment.id,
+        filename=attachment.filename,
+        file_size=attachment.file_size,
+        uploaded_by=UserDisplay.model_validate(current_user) if current_user else None,
+        uploaded_by_id=attachment.uploaded_by,
+        uploaded_at=attachment.uploaded_at,
+    )
 
 
 @router.get(
@@ -90,7 +98,22 @@ async def list_attachments(
 ) -> list[AttachmentRead]:
     await _ensure_study_exists(db, study_id)
     attachments = await attachment_crud.list_attachments(db, study_id, entity_type, entity_id)
-    return list(attachments)
+    user_ids = {a.uploaded_by for a in attachments if a.uploaded_by}
+    users_map = await user_crud.get_users_by_ids(db, user_ids)
+    result: list[AttachmentRead] = []
+    for a in attachments:
+        user = users_map.get(a.uploaded_by)
+        result.append(
+            AttachmentRead(
+                id=a.id,
+                filename=a.filename,
+                file_size=a.file_size,
+                uploaded_by=UserDisplay.model_validate(user) if user else None,
+                uploaded_by_id=a.uploaded_by,
+                uploaded_at=a.uploaded_at,
+            )
+        )
+    return result
 
 
 @router.get(