admin: add server log viewer; fix curl_close() PHP 8.5 deprecation in status.php

- public/admin/logs.php: new page tailing nginx error/access + PHP-FPM logs.
  Selector for log file and line count (50/100/200/500, default 100).
  Lines reversed (newest first), colour-coded by severity, numbered gutter.
  Graceful degradation when exec() unavailable or file unreadable (dev msg).

- templates/admin/head.php: 'Journaux' nav link added after 'Statut'.

- public/admin/status.php: remove curl_close() call deprecated in PHP 8.5
  (no-op since PHP 8.0); replace with unset($ch) to silence the warning
  that was leaking raw text above the page output.

TODO.md

@@ -331,6 +331,6 @@ Goal: rename the tables and column to the canonical M2M pattern (`tags`, `thesis
 - [x] Exclude `.claude` and `.pi` from rsync deploy
 - [x] Update `docs/SERVER_SETUP.md` with correct permissions rationale and troubleshooting
 - [x] Add server status view in admin panel (nginx + php-fpm health, site HTTP check)
-- [ ] Add server log viewer in admin panel (tail nginx error/access logs via SSH or log endpoint)
+- [x] Add server log viewer in admin panel (tail nginx error/access logs via SSH or log endpoint)
 - [ ] Add nginx config deploy flow to admin panel (upload `scripts/deploy-server.sh`, run remotely)
 - [ ] Add admin user management UI (wraps `scripts/manage-admin-users.sh` on server)