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/lodash/_baseSetToString.js

@@ -0,0 +1,22 @@
+var constant = require('./constant'),
+    defineProperty = require('./_defineProperty'),
+    identity = require('./identity');
+
+/**
+ * The base implementation of `setToString` without support for hot loop shorting.
+ *
+ * @private
+ * @param {Function} func The function to modify.
+ * @param {Function} string The `toString` result.
+ * @returns {Function} Returns `func`.
+ */
+var baseSetToString = !defineProperty ? identity : function(func, string) {
+  return defineProperty(func, 'toString', {
+    'configurable': true,
+    'enumerable': false,
+    'value': constant(string),
+    'writable': true
+  });
+};
+
+module.exports = baseSetToString;