feat(frontend): implement TanStack Router with mobile sidebar

- Install and configure TanStack Router for type-safe routing
- Create route structure with __root.tsx layout and individual route files
- Implement mobile-responsive sidebar with collapse functionality
- Add clickable logo in sidebar that navigates to overview page
- Extract Header and Sidebar components from Dashboard for reusability
- Configure Vite with TanStack Router plugin for development
- Update main.tsx to use RouterProvider instead of direct App rendering
- Maintain existing TanStack Query integration seamlessly
- Add proper TypeScript types for all route components
- Implement responsive design with mobile overlay and hamburger menu

This replaces the tab-based navigation with URL-based routing while
maintaining the same user experience and adding powerful features like:
- Bookmarkable URLs (/transactions, /analytics, /notifications)
- Browser back/forward button support
- Direct linking capabilities
- Mobile-responsive sidebar with smooth animations
- Type-safe navigation with auto-completion

frontend/src/routeTree.gen.ts

@@ -0,0 +1,113 @@
+/* eslint-disable */
+
+// @ts-nocheck
+
+// noinspection JSUnusedGlobalSymbols
+
+// This file was automatically generated by TanStack Router.
+// You should NOT make any changes in this file as it will be overwritten.
+// Additionally, you should also exclude this file from your linter and/or formatter to prevent it from being checked or modified.
+
+import { Route as rootRouteImport } from './routes/__root'
+import { Route as TransactionsRouteImport } from './routes/transactions'
+import { Route as NotificationsRouteImport } from './routes/notifications'
+import { Route as AnalyticsRouteImport } from './routes/analytics'
+import { Route as IndexRouteImport } from './routes/index'
+
+const TransactionsRoute = TransactionsRouteImport.update({
+  id: '/transactions',
+  path: '/transactions',
+  getParentRoute: () => rootRouteImport,
+} as any)
+const NotificationsRoute = NotificationsRouteImport.update({
+  id: '/notifications',
+  path: '/notifications',
+  getParentRoute: () => rootRouteImport,
+} as any)
+const AnalyticsRoute = AnalyticsRouteImport.update({
+  id: '/analytics',
+  path: '/analytics',
+  getParentRoute: () => rootRouteImport,
+} as any)
+const IndexRoute = IndexRouteImport.update({
+  id: '/',
+  path: '/',
+  getParentRoute: () => rootRouteImport,
+} as any)
+
+export interface FileRoutesByFullPath {
+  '/': typeof IndexRoute
+  '/analytics': typeof AnalyticsRoute
+  '/notifications': typeof NotificationsRoute
+  '/transactions': typeof TransactionsRoute
+}
+export interface FileRoutesByTo {
+  '/': typeof IndexRoute
+  '/analytics': typeof AnalyticsRoute
+  '/notifications': typeof NotificationsRoute
+  '/transactions': typeof TransactionsRoute
+}
+export interface FileRoutesById {
+  __root__: typeof rootRouteImport
+  '/': typeof IndexRoute
+  '/analytics': typeof AnalyticsRoute
+  '/notifications': typeof NotificationsRoute
+  '/transactions': typeof TransactionsRoute
+}
+export interface FileRouteTypes {
+  fileRoutesByFullPath: FileRoutesByFullPath
+  fullPaths: '/' | '/analytics' | '/notifications' | '/transactions'
+  fileRoutesByTo: FileRoutesByTo
+  to: '/' | '/analytics' | '/notifications' | '/transactions'
+  id: '__root__' | '/' | '/analytics' | '/notifications' | '/transactions'
+  fileRoutesById: FileRoutesById
+}
+export interface RootRouteChildren {
+  IndexRoute: typeof IndexRoute
+  AnalyticsRoute: typeof AnalyticsRoute
+  NotificationsRoute: typeof NotificationsRoute
+  TransactionsRoute: typeof TransactionsRoute
+}
+
+declare module '@tanstack/react-router' {
+  interface FileRoutesByPath {
+    '/transactions': {
+      id: '/transactions'
+      path: '/transactions'
+      fullPath: '/transactions'
+      preLoaderRoute: typeof TransactionsRouteImport
+      parentRoute: typeof rootRouteImport
+    }
+    '/notifications': {
+      id: '/notifications'
+      path: '/notifications'
+      fullPath: '/notifications'
+      preLoaderRoute: typeof NotificationsRouteImport
+      parentRoute: typeof rootRouteImport
+    }
+    '/analytics': {
+      id: '/analytics'
+      path: '/analytics'
+      fullPath: '/analytics'
+      preLoaderRoute: typeof AnalyticsRouteImport
+      parentRoute: typeof rootRouteImport
+    }
+    '/': {
+      id: '/'
+      path: '/'
+      fullPath: '/'
+      preLoaderRoute: typeof IndexRouteImport
+      parentRoute: typeof rootRouteImport
+    }
+  }
+}
+
+const rootRouteChildren: RootRouteChildren = {
+  IndexRoute: IndexRoute,
+  AnalyticsRoute: AnalyticsRoute,
+  NotificationsRoute: NotificationsRoute,
+  TransactionsRoute: TransactionsRoute,
+}
+export const routeTree = rootRouteImport
+  ._addFileChildren(rootRouteChildren)
+  ._addFileTypes<FileRouteTypes>()