daily, weekly, monthly, or none (default to weekly)

this scope is not just a ui update. the system should actually send journal email notifications using postmark.

see that we use POSTMARK_API_KEY in ladderly-io/src/server/mailers/forgotPasswordMailer.ts

we should actually have a mailer for journal notifications

ideally the contributor includes a supabase or vercel cron that checks and sends notifications daily, but I can set up the cron if you get the endpoint working
https://vercel.com/docs/cron-jobs
https://supabase.com/blog/supabase-cron