feat: admin audit logging across all admin actions

- AdminLogger: JSON-lines → /var/log/xamxam.log (prod) / storage/logs/admin.log (dev)
  + best-effort DB mirror to admin_audit_log table
- DB: admin_audit_log table, share_links.is_archived column
- ShareLink: archive() replaces delete(), toggleActive() returns new state,
  listActive()/listArchived() split, validateLink blocks archived slugs
- All action handlers wired: publish, unpublish, visibility, delete, csv/db export,
  tfe add/edit, tags, pages, apropos, form-help, access-request, maintenance,
  settings (formulaire toggles, objet types, smtp update), smtp-test
- acces.php: archive button replaces delete; collapsible archived links section
- setup-server.sh: provision /var/log/xamxam.log (www-data:xamxam 640)

app/public/admin/actions/page.php

@@ -24,10 +24,12 @@ if (!in_array($slug, $allowedSlugs, true)) {
 }
 
 require_once APP_ROOT . '/src/Database.php';
+require_once APP_ROOT . '/src/AdminLogger.php';
 $db = new Database();
 
 try {
     $db->savePage($slug, $content);
+    AdminLogger::make()->logPageEdit($slug);
     App::flash('success', 'Page « ' . htmlspecialchars($slug) . ' » mise à jour.');
 } catch (Exception $e) {
     error_log('page save error: ' . $e->getMessage());