[Web] show external sender addresses regardless of authsource

The extended_sender_acl field sat inside the
`{% if not result.authsource or result.authsource == 'mailcow' %}` block
that hides the local password fields for mailboxes authenticating against
an external identity provider. As a result the "External sender addresses"
input was not rendered at all for keycloak / generic-oidc / ldap mailboxes,
even for a full admin, so those addresses could neither be reviewed nor
edited in the UI while the underlying sender_acl rows stayed active.

Extended sender ACLs are unrelated to local password management. Move the
field out of that block; it stays gated by acl.extend_sender_acl as intended.

Fixes #7365

data/web/templates/edit/mailbox.twig

@@ -267,6 +267,7 @@
                       <small class="text-muted">{{ lang.admin.password_reset_info }}</small>
                     </div>
                   </div>
+                  {% endif %}
                   <div data-acl="{{ acl.extend_sender_acl }}" class="row mb-4">
                     <label class="control-label col-sm-2" for="extended_sender_acl">{{ lang.edit.extended_sender_acl }}</label>
                     <div class="col-sm-10">
@@ -279,7 +280,6 @@
                       {% endif %}
                     </div>
                   </div>
-                  {% endif %}
                   <div class="row">
                     <label class="control-label col-sm-2" for="protocol_access">{{ lang.edit.allowed_protocols }}</label>
                     <div class="col-sm-10">