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/jiti/dist/plugins/babel-plugin-transform-import-meta.d.ts

@@ -0,0 +1,4 @@
+import type { PluginObj } from "@babel/core";
+export declare function TransformImportMetaPlugin(_ctx: any, opts: {
+    filename?: string;
+}): PluginObj;

frontend/node_modules/jiti/dist/plugins/import-meta-env.d.ts

@@ -0,0 +1,5 @@
+/**
+ * Forked from https://github.com/iendeavor/import-meta-env/tree/main/packages/babel 0.4.2 (MIT License - Copyright (c) 2021 Ernest)
+ */
+import type { PluginObj } from "@babel/core";
+export declare function importMetaEnvPlugin({ template, types }: any): PluginObj;