fix(mail): drop contacts from the EAS bundle — Stalwart 404s empty addressbook homes

BackendCombined login is all-or-nothing, and Stalwart returns 404 for
/dav/card/<account>/ when the account's default address book was never
created (it doesn't auto-create on the gateway's PROPFIND the way the
calendar home worked) — so CardDAV killed every otherwise-successful
EAS login. Exchange accounts now bundle mail + calendar; contacts stay
on the Apple-profile CardDAV path. Re-enable BackendCardDAV once
platform-api provisions a default address book at mailbox creation.

Copy/docs aligned: portal hint, SERVICES.md, website FAQ (da+en).

apps/portal/pages/admin/users.vue

@@ -769,7 +769,7 @@ async function submitCreateMailbox() {
                 <template v-else>This member signs in with an external address and has no inbox. Create a mailbox on your domain to give them one — and to enable aliases.</template>
               </p>
               <p v-if="hasMailbox" class="ud-hint">
-                On iPhone and Android the mailbox can also be added as an <strong>Exchange</strong> account — mail, calendar and contacts in one go. Server <Mono>{{ mailHost }}</Mono>, username is the mailbox address. Works in the built-in mail apps (not the Outlook app); on Windows, Outlook syncs the calendar via the free CalDAV Synchronizer add-in.
+                On iPhone and Android the mailbox can also be added as an <strong>Exchange</strong> account — mail and calendar in one go. Server <Mono>{{ mailHost }}</Mono>, username is the mailbox address. Works in the built-in mail apps (not the Outlook app); on Windows, Outlook syncs the calendar via the free CalDAV Synchronizer add-in.
               </p>
             </div>
           </section>