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/folder-key.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 FolderKey = createLucideIcon("FolderKey", [
+  ["circle", { cx: "16", cy: "20", r: "2", key: "1vifvg" }],
+  [
+    "path",
+    {
+      d: "M10 20H4a2 2 0 0 1-2-2V5a2 2 0 0 1 2-2h3.9a2 2 0 0 1 1.69.9l.81 1.2a2 2 0 0 0 1.67.9H20a2 2 0 0 1 2 2v2",
+      key: "3hgo9p"
+    }
+  ],
+  ["path", { d: "m22 14-4.5 4.5", key: "1ef6z8" }],
+  ["path", { d: "m21 15 1 1", key: "1ejcpy" }]
+]);
+
+export { FolderKey as default };
+//# sourceMappingURL=folder-key.js.map