fix: standardize save buttons to use app-action-success class

Replace inconsistent `primary` class with `app-action-success` on all
standalone save buttons so they match the green titlebar convention.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pages/admin/users/edit(default).phtml

@@ -265,7 +265,7 @@ if ($lastLoginAt !== '') {
               <input type="file" name="avatar" accept="image/*">
             </label>
             <div class="grid">
-              <button type="submit" class="primary">
+              <button type="submit" class="app-action-success">
                 <?php e(t('Save')); ?>
               </button>
               <?php if ($hasAvatar): ?>