refactor: 完成多租户架构移除与系统模块重构

1. 移除所有租户相关逻辑：删除租户ID查询参数、租户字段、租户存储相关代码
2. 重构菜单系统：合并platform/system菜单模块，调整菜单作用域为web/app
3. 修复导出接口：统一post请求使用body传参，替换get导出为post
4. 优化权限标识：更新权限路由前缀为module_system
5. 简化菜单过滤逻辑：移除工作区模式判断，直接展示所有菜单
6. 移除租户切换、代签入等无关功能组件与状态
7. 新增用户注册功能与工单导出接口

frontend/web/src/views/module_example/demo/index.vue

@@ -204,13 +204,11 @@ const createInitialFormData = (): DemoForm => ({
 type DemoSearchFormParams = {
   name?: string;
   status?: number;
-  tenant_id?: number;
 } & AuditSearchFormParams;
 
 const searchForm = ref<DemoSearchFormParams>({
   name: undefined,
   status: undefined,
-  tenant_id: undefined,
   created_id: undefined,
   updated_id: undefined,
   created_time: [],
@@ -499,7 +497,6 @@ const handleSearch = async (params: DemoSearchFormParams) => {
   replaceSearchParams({
     name: params.name,
     status: params.status,
-    tenant_id: params.tenant_id,
     created_id: params.created_id ?? undefined,
     updated_id: params.updated_id ?? undefined,
     created_time:
@@ -518,7 +515,6 @@ const onResetSearch = async () => {
   searchForm.value = {
     name: undefined,
     status: undefined,
-    tenant_id: undefined,
     created_id: undefined,
     updated_id: undefined,
     created_time: [],