feat: admin settings page UI/UX pass with WordPress-native patterns

- Header: h1 + logo in a wrapping flex row, hr.wp-header-end before the tabs,
  aria-current on the active tab; own CSS/JS enqueued only on this screen.
- Verbindung: ordered "So verbindest du Claude" steps, copy button (core
  clipboard.js + wp.a11y.speak), Site-Health-style status list, German details.
- Zugriff: roles as form-table fieldset, connections with site date format,
  empty-state row, confirm on revoke; ConnectionUsage records last use via
  WP_Application_Passwords::record_application_password_usage (once a day).
- Tools: plain-language legend, counter as inline notice, groups as core
  postboxes (postbox.js toggles, per-user closed state, summary when closed),
  fixed column widths with new "Art" column, submit above and below.
- Protokoll: site-timezone times with UTC tooltip, result icons, filters with
  labels in the list table nav, retention link to Limits.
- Limits: short labels with units and descriptions; snapshot count hidden but
  preserved.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tests/Stubs/WpListTable.php

@@ -83,7 +83,14 @@ if (! class_exists('WP_List_Table')) {
         {
         }
 
+        /** Like the real class: the top table nav (with extra_tablenav()) comes before the rows. */
         public function display(): void
+        {
+            $this->extra_tablenav('top');
+        }
+
+        /** @param string $which */
+        protected function extra_tablenav($which)
         {
         }
     }