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/export-db.php

@@ -9,6 +9,7 @@ require_once __DIR__ . '/../../../src/AdminAuth.php';
 AdminAuth::requireLogin();
 
 require_once APP_ROOT . '/src/Controllers/ExportController.php';
+require_once APP_ROOT . '/src/AdminLogger.php';
 $controller = ExportController::create();
 
 $dbPath = $controller->getDatabasePath();
@@ -25,5 +26,7 @@ header('Content-Disposition: attachment; filename="' . $filename . '"');
 header('Content-Length: ' . filesize($dbPath));
 header('Cache-Control: no-cache, must-revalidate');
 
+AdminLogger::make()->logDbExport();
+
 readfile($dbPath);
 exit;