fix: /partage/<slug> routing (regex delimiter + nginx location)

public/partage/index.php

@@ -22,7 +22,7 @@ $slug  = $parts[0] ?? '';
 $action = $parts[1] ?? '';
 
 // Validate slug format: YYYYMMDD-XXXXXXXX (17 chars)
-if (!preg_match('/^\d{8}-[A-Z2-7]{8}$/', $slug)) {
+if (!preg_match('#^\d{8}-[A-Z0-9+/]{8}$#', $slug)) {
     App::boot();
     $_SESSION['_flash_error'] = 'Ce lien de partage n\'est pas valide.';
     header('Location: /');