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/axios/lib/helpers/deprecatedMethod.js

@@ -0,0 +1,31 @@
+'use strict';
+
+/*eslint no-console:0*/
+
+/**
+ * Supply a warning to the developer that a method they are using
+ * has been deprecated.
+ *
+ * @param {string} method The name of the deprecated method
+ * @param {string} [instead] The alternate method to use if applicable
+ * @param {string} [docs] The documentation URL to get further details
+ *
+ * @returns {void}
+ */
+export default function deprecatedMethod(method, instead, docs) {
+  try {
+    console.warn(
+      'DEPRECATED method `' +
+        method +
+        '`.' +
+        (instead ? ' Use `' + instead + '` instead.' : '') +
+        ' This method will be removed in a future release.'
+    );
+
+    if (docs) {
+      console.warn('For more information about usage see ' + docs);
+    }
+  } catch (e) {
+    /* Ignore */
+  }
+}