refactor: 移除多租户相关代码，重构为单租户架构

此次提交进行了大规模的架构重构：
1.  移除所有平台租户相关模块和代码，包括租户管理、套餐、订单、发票等功能
2.  将菜单模块从platform迁移到system模块，统一系统功能入口
3.  移除租户隔离相关的模型混入、中间件和配置
4.  简化文件上传、SSE事件总线、定时任务等模块的租户逻辑
5.  重构所有业务schema和模型，移除租户相关字段和关联
6.  清理初始化脚本、模板和常量中的租户相关代码
7.  简化认证和权限控制逻辑，移除数据范围检查相关代码

backend/app/api/v1/module_monitor/online/schema.py

@@ -30,11 +30,7 @@ class DashboardStatsSchema(BaseModel):
     """仪表盘统计数据"""
     online_users: int = 0
     total_users: int = 0
-    total_tenants: int = 0
-    total_orders: int = 0
     today_login_count: int = 0
     today_unique_users: int = 0
     week_user_created: int = 0
-    week_tenant_created: int = 0
-    paid_orders: int = 0
     recent_logins: list[RecentLoginItem] = []

backend/app/api/v1/module_monitor/online/service.py

@@ -5,8 +5,6 @@ from redis.asyncio.client import Redis
 from sqlalchemy import func, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from app.api.v1.module_platform.order.model import OrderModel
-from app.api.v1.module_platform.tenant.model import TenantModel
 from app.api.v1.module_system.log.model import LoginLogModel
 from app.api.v1.module_system.user.model import UserModel
 from app.common.enums import RedisInitKeyConfig
@@ -93,24 +91,6 @@ class OnlineService:
         )
         user_week_count = (await db.execute(users_week_sql)).scalar() or 0
 
-        tenants_sql = select(func.count()).select_from(TenantModel).where(TenantModel.is_deleted.is_(False))
-        tenant_count = (await db.execute(tenants_sql)).scalar() or 0
-
-        tenants_week_sql = (
-            select(func.count()).select_from(TenantModel)
-            .where(TenantModel.is_deleted.is_(False), TenantModel.created_time >= week_start)
-        )
-        tenant_week_count = (await db.execute(tenants_week_sql)).scalar() or 0
-
-        orders_sql = select(func.count()).select_from(OrderModel).where(OrderModel.is_deleted.is_(False))
-        order_count = (await db.execute(orders_sql)).scalar() or 0
-
-        paid_sql = (
-            select(func.count()).select_from(OrderModel)
-            .where(OrderModel.is_deleted.is_(False), OrderModel.status == 1)
-        )
-        paid_count = (await db.execute(paid_sql)).scalar() or 0
-
         today_login_sql = (
             select(func.count()).select_from(LoginLogModel)
             .where(LoginLogModel.created_time >= today_start)
@@ -141,13 +121,9 @@ class OnlineService:
         result = DashboardStatsSchema(
             online_users=online_count,
             total_users=user_count,
-            total_tenants=tenant_count,
-            total_orders=order_count,
             today_login_count=today_login_count,
             today_unique_users=today_unique_count,
             week_user_created=user_week_count,
-            week_tenant_created=tenant_week_count,
-            paid_orders=paid_count,
             recent_logins=recent_logins,
         )
         return result