fix(auth): migrate from next-auth to better-auth (#1453)

app/(auth)/auth.config.ts

@@ -1,14 +0,0 @@
-import type { NextAuthConfig } from "next-auth";
-
-export const authConfig = {
-  basePath: "/api/auth",
-  pages: {
-    signIn: "/login",
-    newUser: "/",
-  },
-  providers: [
-    // added later in auth.ts since it requires bcrypt which is only compatible with Node.js
-    // while this file is also used in non-Node.js environments
-  ],
-  callbacks: {},
-} satisfies NextAuthConfig;