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/@babel/runtime/helpers/esm/inherits.js

@@ -0,0 +1,14 @@
+import setPrototypeOf from "./setPrototypeOf.js";
+function _inherits(t, e) {
+  if ("function" != typeof e && null !== e) throw new TypeError("Super expression must either be null or a function");
+  t.prototype = Object.create(e && e.prototype, {
+    constructor: {
+      value: t,
+      writable: !0,
+      configurable: !0
+    }
+  }), Object.defineProperty(t, "prototype", {
+    writable: !1
+  }), e && setPrototypeOf(t, e);
+}
+export { _inherits as default };