feat: 操作日志系统 + 日期修复 + 协同去重 + 主题持久化 + 计划自动完成

本次累积提交包含以下功能：

1. 修复：el-date-picker 缺失 value-format 导致日期保存偏移（8处）
2. 新增：协同拜访 visit_group_id 去重机制（完整副本 + 周报合并 + 亮灯去重）
3. 新增：计划自动完成（创建计划检测已有拜访 / 编辑拜访触发）
4. 新增：拜访表单选择客户后自动预填过期计划内容
5. 新增：移动端主题切换按钮 + 后端持久化
6. 新增：操作日志系统 (audit_logs)，全覆盖 8 个模块 CRUD
7. 新增：PC端「我的数据」支局长/领导视角客户经理列

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

backend/app/api/customers.py

@@ -20,6 +20,7 @@ from app.models.mini_business import MiniBusiness
 from app.models.key_visit import KeyVisit
 from app.models.daily_note import DailyNote
 from app.models.user import User
+from app.utils.audit import log_audit
 from app.schemas.customer import (
     CustomerCreate, CustomerUpdate, CustomerOut, CustomerListOut, CustomerListResponse,
     ContactCreate, ContactOut, AssignmentCreate, AssignmentOut, BatchAssignRequest,
@@ -399,6 +400,10 @@ async def create_customer(
     ))
     await db.commit()
 
+    # Audit log
+    await log_audit(db, "customer", customer.id, customer.name, "create", current_user["user_id"], current_user["name"])
+    await db.commit()
+
     result = await db.execute(
         select(Customer).where(Customer.id == customer.id).options(selectinload(Customer.contacts))
     )
@@ -470,6 +475,10 @@ async def update_customer(
 
     await db.commit()
 
+    # Audit log
+    await log_audit(db, "customer", uuid_mod.UUID(customer_id), customer.name, "update", current_user["user_id"], current_user["name"])
+    await db.commit()
+
     result = await db.execute(
         select(Customer).where(Customer.id == customer.id).options(selectinload(Customer.contacts))
     )
@@ -486,8 +495,12 @@ async def delete_customer(
     customer = result.scalar_one_or_none()
     if not customer:
         raise HTTPException(status_code=404, detail="Customer not found")
+    cust_name = customer.name
     await db.delete(customer)
     await db.commit()
+    # Audit log
+    await log_audit(db, "customer", uuid_mod.UUID(customer_id), cust_name, "delete", current_user["user_id"], current_user["name"])
+    await db.commit()
     return {"detail": "deleted"}
 
 
@@ -715,3 +728,33 @@ async def assign_manager(
     await db.commit()
     await db.refresh(assignment)
     return assignment
+
+
+@router.get("/{customer_id}/overdue-plans")
+async def get_overdue_plans(
+    customer_id: str,
+    current_user: dict = Depends(get_current_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """Return the latest overdue (plan_date < today) and still '计划中' plan for a customer.
+    Used by the frontend to pre-fill visit forms with pending plan content."""
+    from app.utils.timezone import today_cst
+    today = today_cst()
+    result = await db.execute(
+        select(WorkPlan).where(
+            WorkPlan.customer_id == uuid_mod.UUID(customer_id),
+            WorkPlan.status == "计划中",
+            WorkPlan.plan_date < today,
+        ).order_by(WorkPlan.plan_date.desc()).limit(1)
+    )
+    plan = result.scalar_one_or_none()
+    if not plan:
+        return {"plan": None}
+    return {
+        "plan": {
+            "id": str(plan.id),
+            "plan_content": plan.plan_content,
+            "plan_date": str(plan.plan_date),
+            "manager_id": str(plan.manager_id),
+        }
+    }