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>

modules/helpdesk/web/js/helpdesk-detail.js

@@ -848,14 +848,6 @@ function init(container) {
         onContentLoaded: (contentEl) => {
           try { initHelpdeskTicket(contentEl); } catch (err) { console.warn('[helpdesk-detail] initHelpdeskTicket failed', err); }
         },
-        labels: {
-          close: labels.drawerClose || 'Close',
-          previous: labels.drawerPrev || 'Previous',
-          next: labels.drawerNext || 'Next',
-          openFull: labels.drawerOpenFull || 'Open full page',
-          loading: labels.drawerLoading || 'Loading',
-          error: labels.drawerError || 'Failed to load',
-        },
       });
     } finally {
       ticketsGridInitializing = false;