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/file-stack.js

@@ -0,0 +1,24 @@
+/**
+ * @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 FileStack = createLucideIcon("FileStack", [
+  ["path", { d: "M16 2v5h5", key: "kt2in0" }],
+  [
+    "path",
+    {
+      d: "M21 6v6.5c0 .8-.7 1.5-1.5 1.5h-7c-.8 0-1.5-.7-1.5-1.5v-9c0-.8.7-1.5 1.5-1.5H17l4 4z",
+      key: "1km23n"
+    }
+  ],
+  ["path", { d: "M7 8v8.8c0 .3.2.6.4.8.2.2.5.4.8.4H15", key: "16874u" }],
+  ["path", { d: "M3 12v8.8c0 .3.2.6.4.8.2.2.5.4.8.4H11", key: "k2ox98" }]
+]);
+
+export { FileStack as default };
+//# sourceMappingURL=file-stack.js.map