refactor(ui): consistent outline/fill icons in topbar, remove dropdown chevrons, truncate breadcrumbs

Use Stripe pattern: outline icons by default, filled for active state
(bookmarks bookmarked, notifications unread). Remove chevron arrows
from tenant/user dropdowns. Add max-width with ellipsis to breadcrumb
items to prevent overflow.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

modules/notifications/templates/topbar-notification-bell.phtml

@@ -9,7 +9,7 @@ $unreadCount = (int) ($notifNav['unread_count'] ?? 0);
         <summary
             aria-label="<?php e(t('Notifications')); ?>"
             >
-            <i class="bi bi-bell"></i>
+            <i class="bi <?php e($unreadCount > 0 ? 'bi-bell-fill' : 'bi-bell'); ?>"></i>
             <?php if ($unreadCount > 0): ?>
                 <span class="app-notification-badge" data-notification-badge><?php e($unreadCount > 99 ? '99+' : $unreadCount); ?></span>
             <?php else: ?>