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/javascript/dashboard/routes/dashboard/onboarding/Index.vue

@@ -134,7 +134,7 @@ const populateFormFields = () => {
 
   if (!locale.value) locale.value = detectBestLocale();
   if (!website.value) {
-    website.value = account?.domain || brandInfo?.domain || '';
+    website.value = attrs.website || brandInfo?.domain || '';
   }
   if (!timezone.value) {
     timezone.value =
@@ -216,7 +216,7 @@ const handleSubmit = async () => {
     await updateAccount({
       name: accountName.value,
       locale: locale.value,
-      domain: website.value,
+      website: website.value,
       industry: industry.value,
       company_size: companySize.value,
       timezone: timezone.value,