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/message-square-diff.js

@@ -0,0 +1,18 @@
+/**
+ * @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 MessageSquareDiff = createLucideIcon("MessageSquareDiff", [
+  ["path", { d: "m5 19-2 2V5a2 2 0 0 1 2-2h14a2 2 0 0 1 2 2v10a2 2 0 0 1-2 2", key: "1xuzuj" }],
+  ["path", { d: "M9 10h6", key: "9gxzsh" }],
+  ["path", { d: "M12 7v6", key: "lw1j43" }],
+  ["path", { d: "M9 17h6", key: "r8uit2" }]
+]);
+
+export { MessageSquareDiff as default };
+//# sourceMappingURL=message-square-diff.js.map