feat(frontend): add API client, layout, and routing

- Create Axios-based API client with sources, jobs, and dashboard endpoints
- Add responsive Layout component with navigation sidebar
- Set up React Router with Dashboard, Backups, and Settings routes
- Configure TanStack Query provider with default options
- Use lucide-react for navigation icons

frontend/node_modules/side-channel-list/list.d.ts

@@ -0,0 +1,14 @@
+type ListNode<T, K> = {
+	key: K;
+	next: undefined | ListNode<T, K>;
+	value: T;
+};
+type RootNode<T, K> = {
+	next: undefined | ListNode<T, K>;
+};
+
+export function listGetNode<T, K>(list: RootNode<T, K>, key: ListNode<T, K>['key'], isDelete?: boolean): ListNode<T, K> | undefined;
+export function listGet<T, K>(objects: undefined | RootNode<T, K>, key: ListNode<T, K>['key']): T | undefined;
+export function listSet<T, K>(objects: RootNode<T, K>, key: ListNode<T, K>['key'], value: T): void;
+export function listHas<T, K>(objects: undefined | RootNode<T, K>, key: ListNode<T, K>['key']): boolean;
+export function listDelete<T, K>(objects: undefined | RootNode<T, K>, key: ListNode<T, K>['key']): ListNode<T, K> | undefined;