remove duplicate BETTER_AUTH_* default env variables (#37)

.env.example

@@ -20,9 +20,6 @@ RESEND_API_KEY="re_123456789"
 # Optional: Create an audience in Resend dashboard
 RESEND_AUDIENCE_ID="aud_123456789"
 
-BETTER_AUTH_SECRET=
-BETTER_AUTH_URL=http://localhost:3000
-
 # OpenPanel Integration
 # Get these from your OpenPanel dashboard
 OPENPANEL_SECRET_KEY="op_sk_123456789"