feat(auth): implement user authentication system

backend/node_modules/escalade/index.d.mts

@@ -0,0 +1,11 @@
+type Promisable<T> = T | Promise<T>;
+
+export type Callback = (
+	directory: string,
+	files: string[],
+) => Promisable<string | false | void>;
+
+export default function (
+	directory: string,
+	callback: Callback,
+): Promise<string | void>;