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/_stackClear.js

@@ -0,0 +1,15 @@
+var ListCache = require('./_ListCache');
+
+/**
+ * Removes all key-value entries from the stack.
+ *
+ * @private
+ * @name clear
+ * @memberOf Stack
+ */
+function stackClear() {
+  this.__data__ = new ListCache;
+  this.size = 0;
+}
+
+module.exports = stackClear;