refactor(ui): move detail drawer chrome to a server-rendered partial

The drawer chrome used to be built in JS via a 50-line innerHTML string
and needed every caller to plumb through a labels object sourced from
per-page PHP config. That diverged from the codebase convention — the
confirm dialog, search dialog and session warning are all PHP partials
mounted once in templates/default.phtml. The drawer now follows the
same pattern: templates/partials/app-detail-drawer.phtml renders the
markup with t() labels, default.phtml mounts it inside the logged-in
shell, and the JS only attaches behavior via the [data-detail-drawer]
selector.

Knock-on cleanup: ensureDrawerElement and resolveLabels disappear from
the JS, all three initDetailDrawer callers (admin/users, address book,
helpdesk debitor) drop their labels parameter, and the matching dead
'drawerClose'/'drawerPrev'/… entries leave the per-page PHP grid configs.
The drawer also gains a clean fallback when the partial is missing
(console warn + null return), so logged-out edges can't crash.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -131,12 +131,6 @@ $pageConfig = [
     'bulkSendAccessConfirm' => t('Send access emails to selected users?'),
     'bulkAccessPdfConfirm' => t('Generate access PDFs for selected users?'),
     'primaryTenant' => t('Primary tenant'),
-    'drawerClose' => t('Close'),
-    'drawerPrev' => t('Previous'),
-    'drawerNext' => t('Next'),
-    'drawerOpenFull' => t('Open full page'),
-    'drawerLoading' => t('Loading'),
-    'drawerError' => t('Failed to load'),
     'bulkMessages' => [
       'activate' => [
         'success' => t('%d users activated'),