feat: integrate @t3-oss/env for environment variable management across the application

packages/auth/src/client.ts

@@ -1,5 +1,8 @@
 import { createAuthClient } from "better-auth/react";
+import { keys } from "./keys";
+
+const { NEXT_PUBLIC_BETTER_AUTH_URL } = keys();
 
 export const { signIn, signUp, useSession } = createAuthClient({
-  baseURL: process.env.NEXT_PUBLIC_BETTER_AUTH_URL!,
-}); 
+  baseURL: NEXT_PUBLIC_BETTER_AUTH_URL,
+});