feat: 上游显示真实发送人 — 从task_logs追溯created_by

backend/app/schemas/task.py

@@ -116,6 +116,7 @@ class TaskSummaryResponse(BaseModel):
     received_at: datetime | None = None
     completed_at: datetime | None = None
     created_at: datetime
+    created_by: str | None = None   # 谁创建的（从task_logs追溯）
 
     model_config = {"from_attributes": True}
 
@@ -140,6 +141,7 @@ class TaskResponse(BaseModel):
     created_at: datetime
     child_tasks: list[TaskResponse] = []
     records: list[TaskRecordResponse] = []
+    created_by: str | None = None   # 谁创建的（从task_logs追溯）
 
     model_config = {"from_attributes": True}