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/lucide-react/dist/esm/icons/files.js

@@ -0,0 +1,23 @@
+/**
+ * @license lucide-react v0.303.0 - ISC
+ *
+ * This source code is licensed under the ISC license.
+ * See the LICENSE file in the root directory of this source tree.
+ */
+
+import createLucideIcon from '../createLucideIcon.js';
+
+const Files = createLucideIcon("Files", [
+  [
+    "path",
+    {
+      d: "M15.5 2H8.6c-.4 0-.8.2-1.1.5-.3.3-.5.7-.5 1.1v12.8c0 .4.2.8.5 1.1.3.3.7.5 1.1.5h9.8c.4 0 .8-.2 1.1-.5.3-.3.5-.7.5-1.1V6.5L15.5 2z",
+      key: "cennsq"
+    }
+  ],
+  ["path", { d: "M3 7.6v12.8c0 .4.2.8.5 1.1.3.3.7.5 1.1.5h9.8", key: "ms809a" }],
+  ["path", { d: "M15 2v5h5", key: "qq6kwv" }]
+]);
+
+export { Files as default };
+//# sourceMappingURL=files.js.map