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/calendar-clock.js

@@ -0,0 +1,20 @@
+/**
+ * @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 CalendarClock = createLucideIcon("CalendarClock", [
+  ["path", { d: "M21 7.5V6a2 2 0 0 0-2-2H5a2 2 0 0 0-2 2v14a2 2 0 0 0 2 2h3.5", key: "1osxxc" }],
+  ["path", { d: "M16 2v4", key: "4m81vk" }],
+  ["path", { d: "M8 2v4", key: "1cmpym" }],
+  ["path", { d: "M3 10h5", key: "r794hk" }],
+  ["path", { d: "M17.5 17.5 16 16.25V14", key: "re2vv1" }],
+  ["path", { d: "M22 16a6 6 0 1 1-12 0 6 6 0 0 1 12 0Z", key: "ame013" }]
+]);
+
+export { CalendarClock as default };
+//# sourceMappingURL=calendar-clock.js.map