Add autosave draft system for partage form with HTMX-based session persistence

- New fragment endpoint POST/GET /partage/fragments/draft.php:
  saves all form fields to PHP session, excludes file/csrf/slug fields
  GET returns JSON for JS hydration on page load
  rotates both global CSRF and share CSRF tokens in sync

- form.php accepts optional $formExtraAttrs and $showAutosaveStatus:
  allows injecting HTMX attributes and 'Brouillon enregistré' indicator

- renderShareLinkForm adds hx-post with change/input debounce trigger,
  loads autosave-handler.js, hydrate fields from draft on page load

- Draft cleared on successful form submission in handleShareLinkSubmission

- autosave-handler.js now also updates share_link_token hidden input
  when rotating CSRF token (partage form uses both csrf_token and share_link_token)

- Added .autosave-status CSS to form.css (was admin.css-only)

- Updated fragment routing to accept GET requests (needed for draft hydration)

app/src/AppLogger.php

@@ -8,15 +8,8 @@
  */
 class AppLogger
 {
-    private string $logDir;
-    private string $logFile;
-
-    public function __construct(?string $logDir = null)
+    public function __construct()
     {
-        $this->logDir = $logDir ?? (defined('STORAGE_ROOT') ? STORAGE_ROOT . '/logs' : __DIR__ . '/../storage/logs');
-
-        // Keep for backward compat — actual file I/O is now handled by Monolog via Logger::get('app')
-        $this->logFile = $this->logDir . '/form-submissions.log';
     }
 
     /**