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/lib/api.ts

@@ -36,8 +36,14 @@ export const apiClient = {
   },
 
   // Update account details
-  updateAccount: async (id: string, updates: AccountUpdate): Promise<{ id: string; name?: string }> => {
-    const response = await api.put<ApiResponse<{ id: string; name?: string }>>(`/accounts/${id}`, updates);
+  updateAccount: async (
+    id: string,
+    updates: AccountUpdate,
+  ): Promise<{ id: string; name?: string }> => {
+    const response = await api.put<ApiResponse<{ id: string; name?: string }>>(
+      `/accounts/${id}`,
+      updates,
+    );
     return response.data.data;
   },