Stop the onboarding flow from writing the user's company website into
`accounts.domain`. That column is reserved for the inbound email domain
used to construct reply-to addresses (`reply+<uuid>@<domain>`), and
silently overloading it from onboarding was breaking email continuity
for accounts whose domain MX didn't point at Chatwoot's inbound —
customer replies were going to an unreachable address.
The website value now lives in `custom_attributes.website`, which is
what the rest of the app already treats as the "company website" field.
