feat(holiday-calendar): implement holiday calendar component with CRUD functionality

- Added a new `HolidayCalendar` component for managing custom and official holidays.
- Integrated holiday type fetching and population logic to streamline holiday management.
- Enhanced UI with modals for creating, editing, and deleting holidays, including validation and user feedback.
- Updated styles for improved visual presentation and user interaction.
- Refactored sidebar and routes to accommodate new component structure and localization updates.

worklenz-frontend/src/lib/admin-center-constants.ts

@@ -0,0 +1,69 @@
+import {
+  AppstoreOutlined,
+  CreditCardOutlined,
+  ProfileOutlined,
+  TeamOutlined,
+  UserOutlined,
+  SettingOutlined,
+} from '@/shared/antd-imports';
+import React, { ReactNode, lazy } from 'react';
+const Overview = lazy(() => import('../pages/admin-center/overview/overview'));
+const Users = lazy(() => import('../pages/admin-center/users/users'));
+const Teams = lazy(() => import('../pages/admin-center/teams/teams'));
+const Billing = lazy(() => import('../pages/admin-center/billing/billing'));
+const Projects = lazy(() => import('../pages/admin-center/projects/projects'));
+const Settings = lazy(() => import('../pages/admin-center/settings/Settings'));
+
+// type of a menu item in admin center sidebar
+type AdminCenterMenuItems = {
+  key: string;
+  name: string;
+  endpoint: string;
+  icon: ReactNode;
+  element: ReactNode;
+};
+// settings all element items use for sidebar and routes
+export const adminCenterItems: AdminCenterMenuItems[] = [
+  {
+    key: 'overview',
+    name: 'overview',
+    endpoint: 'overview',
+    icon: React.createElement(AppstoreOutlined),
+    element: React.createElement(Overview),
+  },
+  {
+    key: 'users',
+    name: 'users',
+    endpoint: 'users',
+    icon: React.createElement(UserOutlined),
+    element: React.createElement(Users),
+  },
+  {
+    key: 'teams',
+    name: 'teams',
+    endpoint: 'teams',
+    icon: React.createElement(TeamOutlined),
+    element: React.createElement(Teams),
+  },
+  {
+    key: 'projects',
+    name: 'projects',
+    endpoint: 'projects',
+    icon: React.createElement(ProfileOutlined),
+    element: React.createElement(Projects),
+  },
+  {
+    key: 'billing',
+    name: 'billing',
+    endpoint: 'billing',
+    icon: React.createElement(CreditCardOutlined),
+    element: React.createElement(Billing),
+  },
+  {
+    key: 'settings',
+    name: 'settings',
+    endpoint: 'settings',
+    icon: React.createElement(SettingOutlined),
+    element: React.createElement(Settings),
+  },
+];