Refactor: Split Sidebar.tsx into smaller components

Refactored the Sidebar component into smaller, more manageable files to improve code organization and maintainability.

Fix sidebar auto-expansion issue
Ensured the sidebar's collapsed state is maintained when navigating between pages.

application/src/components/dashboard/sidebar/index.ts

@@ -0,0 +1,6 @@
+
+export { SidebarHeader } from './SidebarHeader';
+export { MainNavigation } from './MainNavigation';
+export { MenuItem } from './MenuItem';
+export { SettingsPanel } from './SettingsPanel';
+export { mainMenuItems, settingsMenuItems } from './navigationData';