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/backpack.js

@@ -0,0 +1,22 @@
+/**
+ * @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 Backpack = createLucideIcon("Backpack", [
+  [
+    "path",
+    { d: "M4 10a4 4 0 0 1 4-4h8a4 4 0 0 1 4 4v10a2 2 0 0 1-2 2H6a2 2 0 0 1-2-2Z", key: "wvr1b5" }
+  ],
+  ["path", { d: "M9 6V4a2 2 0 0 1 2-2h2a2 2 0 0 1 2 2v2", key: "donm21" }],
+  ["path", { d: "M8 21v-5a2 2 0 0 1 2-2h4a2 2 0 0 1 2 2v5", key: "xk3gvk" }],
+  ["path", { d: "M8 10h8", key: "c7uz4u" }],
+  ["path", { d: "M8 18h8", key: "1no2b1" }]
+]);
+
+export { Backpack as default };
+//# sourceMappingURL=backpack.js.map