feat: 工作计划状态自动流转

- 抽取 auto_complete_work_plans() 可复用函数到 visits service
- POST/PUT 拜访均触发自动完成（更新场景解决补录问题）
- Excel 导入旧周报时也触发自动完成
- 逾期计划自动取消：plan_date < today 且无匹配拜访→已取消
- edit_log 记录区分三种来源：拜访自动完成/拜访更新自动完成/旧周报导入自动完成/逾期自动取消

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

backend/app/services/excel_import.py

@@ -203,6 +203,13 @@ async def import_from_excel(db: AsyncSession, file_bytes: bytes, manager_id: uui
                 db.add(visit)
                 stats["visits"] += 1
 
+                # Auto-complete matching work plans
+                from app.services.visits import auto_complete_work_plans
+                await auto_complete_work_plans(
+                    db, customer_id, visit_date,
+                    mgr_name, "旧周报导入自动完成",
+                )
+
                 # Update customer's last_visit_date for light board
                 cust = await db.get(Customer, customer_id)
                 if cust and (not cust.last_visit_date or visit_date > cust.last_visit_date):