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/_hashDelete.js

@@ -0,0 +1,17 @@
+/**
+ * Removes `key` and its value from the hash.
+ *
+ * @private
+ * @name delete
+ * @memberOf Hash
+ * @param {Object} hash The hash to modify.
+ * @param {string} key The key of the value to remove.
+ * @returns {boolean} Returns `true` if the entry was removed, else `false`.
+ */
+function hashDelete(key) {
+  var result = this.has(key) && delete this.__data__[key];
+  this.size -= result ? 1 : 0;
+  return result;
+}
+
+module.exports = hashDelete;