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/_copySymbolsIn.js

@@ -0,0 +1,16 @@
+var copyObject = require('./_copyObject'),
+    getSymbolsIn = require('./_getSymbolsIn');
+
+/**
+ * Copies own and inherited symbols of `source` to `object`.
+ *
+ * @private
+ * @param {Object} source The object to copy symbols from.
+ * @param {Object} [object={}] The object to copy symbols to.
+ * @returns {Object} Returns `object`.
+ */
+function copySymbolsIn(source, object) {
+  return copyObject(source, getSymbolsIn(source), object);
+}
+
+module.exports = copySymbolsIn;