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/key_visits.py

@@ -63,7 +63,7 @@ async def create_key_visit(
         planned_date=data.planned_date,
         planned_visitor=data.planned_visitor,
         visit_target=data.visit_target,
-        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"]),
     )
     init_entry(k, current_user["name"])
     db.add(k)
@@ -87,6 +87,8 @@ async def update_key_visit(
 
     old_snapshot = {"customer_id": str(k.customer_id), "urgency_level": k.urgency_level, "description": k.description, "progress_status": k.progress_status, "planned_date": k.planned_date, "planned_visitor": k.planned_visitor, "visit_target": k.visit_target}
     update_data = data.model_dump(exclude_unset=True)
+    if current_user["role"] not in ("director", "leader"):
+        update_data.pop("manager_id", None)
     for key, v in update_data.items():
         setattr(k, key, v)
     new_snapshot = {"customer_id": str(k.customer_id), "urgency_level": k.urgency_level, "description": k.description, "progress_status": k.progress_status, "planned_date": k.planned_date, "planned_visitor": k.planned_visitor, "visit_target": k.visit_target}