feat: 支局长/分管领导可为任意客户经理代填记录

后端:
- 5个模块的 Create/Update schema 新增可选 manager_id 字段
- POST 端点: director/leader 可指定 manager_id，manager 角色自动用自身
- PUT 端点: director/leader 可修改 manager_id，manager 角色禁止修改

前端（移动端+桌面端共10个页面）:
- 支局长/领导可见「客户经理」下拉选择框
- 创建和编辑时均可指定记录归属的客户经理
- 涵盖今日拜访、今日纪要、工作计划、商机跟单、要客拜访五个模块

Co-Authored-By: Claude <noreply@anthropic.com>

backend/app/api/work_plans.py

@@ -58,7 +58,7 @@ async def create_work_plan(
         customer_id=data.customer_id,
         plan_content=data.plan_content,
         plan_date=parse_date(data.plan_date),
-        manager_id=uuid.UUID(current_user["user_id"]),
+        manager_id=data.manager_id if (current_user["role"] in ("director", "leader") and data.manager_id) else uuid.UUID(current_user["user_id"]),
         status=data.status,
     )
     init_entry(wp, current_user["name"])
@@ -83,6 +83,8 @@ async def update_work_plan(
 
     old_snapshot = {"customer_id": str(wp.customer_id), "plan_content": wp.plan_content, "plan_date": str(wp.plan_date), "status": wp.status}
     update_data = data.model_dump(exclude_unset=True)
+    if current_user["role"] not in ("director", "leader"):
+        update_data.pop("manager_id", None)
     if "plan_date" in update_data and update_data["plan_date"]:
         update_data["plan_date"] = parse_date(update_data["plan_date"])
     for k, v in update_data.items():