feat: 支持先绑定设备后关联儿童档案

- 绑定模型新增 owner_user_id，支持 child_id 为空\n- 新增绑定后设置儿童接口 /bindings/{device_id}/child\n- 前端绑定页改为先绑设备后补充儿童\n- 补充数据库迁移脚本与 DAO 测试用例

mini-program/app/routers/bindings.py

@@ -1,4 +1,5 @@
 import logging
+from datetime import datetime
 
 from fastapi import APIRouter, Depends, HTTPException, Request, status
 from pydantic import BaseModel
@@ -19,7 +20,7 @@ logger = logging.getLogger("app.bindings")
 
 class BindStartRequest(BaseModel):
     device_id: str
-    child_id: int
+    child_id: int | None = None
 
 
 class BindStartResponse(BaseModel):
@@ -34,21 +35,21 @@ class BindConfirmRequest(BaseModel):
 
 class BindConfirmResponse(BaseModel):
     device_id: str
-    child_id: int
+    child_id: int | None
 
 
 class BindingGetResponse(BaseModel):
     device_id: str
-    child_id: int
+    child_id: int | None
     status: int
-    bound_at: str
+    bound_at: datetime
 
 
 class BindHistoryItem(BaseModel):
     device_id: str
-    child_id: int
-    bound_at: str
-    unbound_at: str | None
+    child_id: int | None
+    bound_at: datetime
+    unbound_at: datetime | None
 
 
 class BindHistoryResponse(BaseModel):
@@ -86,11 +87,15 @@ def confirm_bind(
 
 class DirectBindRequest(BaseModel):
     device_id: str
-    child_id: int
+    child_id: int | None = None
 
 
 class DirectBindResponse(BaseModel):
     device_id: str
+    child_id: int | None
+
+
+class BindSetChildRequest(BaseModel):
     child_id: int
 
 
@@ -106,6 +111,22 @@ def direct_bind(
     return DirectBindResponse(**result)
 
 
+@router.patch("/{device_id}/child", response_model=DirectBindResponse)
+def set_binding_child(
+    device_id: str,
+    payload: BindSetChildRequest,
+    request: Request,
+    current_user_id: int = Depends(get_current_user_id),
+    db=Depends(get_db_session),
+) -> DirectBindResponse:
+    service = BindingService(db)
+    try:
+        result = service.set_binding_child(device_id=device_id, child_id=payload.child_id, user_id=current_user_id)
+    except ValueError as e:
+        raise HTTPException(status_code=404, detail=str(e))
+    return DirectBindResponse(**result)
+
+
 @router.get("/current", response_model=BindingGetResponse)
 def get_current_binding(
     request: Request,
@@ -154,11 +175,9 @@ def get_bind_history(
     current_user_id: int = Depends(get_current_user_id),
     db=Depends(get_db_session),
 ) -> BindHistoryResponse:
-    from datetime import datetime
-
     cursor_dt = datetime.fromisoformat(cursor) if cursor else None
     service = BindingService(db)
     rows, has_more = service.list_history(device_id, limit, cursor_dt)
     next_cursor = rows[-1]["bound_at"].isoformat() if has_more and rows else None
     items = [BindHistoryItem(**row) for row in rows]
-    return BindHistoryResponse(items=items, total=len(items), next_cursor=next_cursor)
+    return BindHistoryResponse(items=items, total=len(items), next_cursor=next_cursor)