Fix

backend/src/routes/notifications.js

@@ -46,7 +46,9 @@ router.post('/broadcast', requireAdmin, (req, res) => {
   );
 
   let targets;
-  if (user_id) {
+  if (user_id === 'admins') {
+    targets = db.prepare("SELECT id FROM users WHERE role = 'admin'").all();
+  } else if (user_id) {
     const u = db.prepare('SELECT id FROM users WHERE id = ?').get(user_id);
     if (!u) return res.status(404).json({ error: 'Utilisateur introuvable' });
     targets = [u];