feat: don't let onboarding write domain (#14442)

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.

app/controllers/api/v1/accounts_controller.rb

@@ -111,7 +111,7 @@ class Api::V1::AccountsController < Api::BaseController
   end
 
   def custom_attributes_params
-    params.permit(:industry, :company_size, :timezone, :referral_source, :user_role)
+    params.permit(:industry, :company_size, :timezone, :referral_source, :user_role, :website)
   end
 
   def settings_params