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/scheduler.py

@@ -168,9 +168,33 @@ async def check_overdue_plans(db: AsyncSession) -> dict:
 
         await wecom_client.send_text_message([user.wecom_userid], content)
 
+    # ── Auto-cancel overdue plans that have no matching visit ──
+    from app.utils.edit_log import append_entry as append_edit_log
+    auto_cancelled = 0
+    for plan in overdue:
+        has_visit = await db.execute(
+            select(Visit).where(
+                Visit.customer_id == plan.customer_id,
+                Visit.visit_date >= plan.plan_date,
+            )
+        )
+        if not has_visit.scalar():
+            plan.status = "已取消"
+            append_edit_log(plan, "系统", [{
+                "field": "status",
+                "from": "计划中",
+                "to": "已取消",
+                "reason": "逾期自动取消",
+            }])
+            auto_cancelled += 1
+
+    if auto_cancelled:
+        await db.commit()
+
     return {
         "status": "ok",
         "date": str(today),
         "overdue": len(overdue),
+        "auto_cancelled": auto_cancelled,
         "managers_affected": len(by_manager),
     }