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/api/visits.py

@@ -161,17 +161,11 @@ async def create_visit(
         db.add(customer)
 
     # Auto-complete matching work plans for this customer
-    from app.models.work_plan import WorkPlan
-    plans_result = await db.execute(
-        select(WorkPlan).where(
-            WorkPlan.customer_id == data.customer_id,
-            WorkPlan.status == "计划中",
-            WorkPlan.plan_date <= parse_date(data.visit_date),
-        )
+    from app.services.visits import auto_complete_work_plans
+    await auto_complete_work_plans(
+        db, data.customer_id, parse_date(data.visit_date),
+        current_user["name"], "拜访自动完成",
     )
-    for plan in plans_result.scalars().all():
-        plan.status = "已完成"
-        append_entry(plan, current_user["name"], [{"field": "status", "from": "计划中", "to": "已完成", "reason": "拜访自动完成"}])
 
     # Create draft copies for companions
     for companion_id in data.companions:
@@ -237,6 +231,15 @@ async def update_visit(
 
     await db.commit()
     await db.refresh(visit)
+
+    # Auto-complete matching work plans after visit update
+    from app.services.visits import auto_complete_work_plans
+    await auto_complete_work_plans(
+        db, visit.customer_id, visit.visit_date,
+        current_user["name"], "拜访更新自动完成",
+    )
+    await db.commit()
+
     return await _enrich_visit(visit, db)