User found that adding bet365.com (which is in the 208k global filter)
silently took a custom-domain slot — they paid a slot for something
the global blocklist already covered. Two pieces:
1. backend/custom-domains/index.post.ts: before any slot-limit check or
DB insert, look the domain up in blocklist_domain (active rows). If
present, return 200 { alreadyGlobal: true, domain }. No row gets
written, no slot consumed. The existing frontend hook + AddSheet
already handle the alreadyGlobal flag — they surface the
"bereits global blockiert" alert and don't refresh as if the entry
landed in the user's list.
2. blocker.tsx default mailOpen state flipped from true to false so the
Eigene Mails section starts collapsed on page load. Domains stays
the primary affordance; mail-patterns are an opt-in expansion.
f19d00017a