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-check.js

@@ -0,0 +1,19 @@
+/**
+ * @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 CalendarCheck = createLucideIcon("CalendarCheck", [
+  ["rect", { width: "18", height: "18", x: "3", y: "4", rx: "2", ry: "2", key: "eu3xkr" }],
+  ["line", { x1: "16", x2: "16", y1: "2", y2: "6", key: "m3sa8f" }],
+  ["line", { x1: "8", x2: "8", y1: "2", y2: "6", key: "18kwsl" }],
+  ["line", { x1: "3", x2: "21", y1: "10", y2: "10", key: "xt86sb" }],
+  ["path", { d: "m9 16 2 2 4-4", key: "19s6y9" }]
+]);
+
+export { CalendarCheck as default };
+//# sourceMappingURL=calendar-check.js.map