fix(api): bringAddItems() missing $input/$items decode — always returned 0

bringAddItems() used $input and $items without ever decoding the request
body. $items was undefined (null) so the foreach never ran, every call
returned added=0 skipped=0 regardless of what was sent.

Added:
  $input = json_decode(file_get_contents('php://input'), true) ?? [];
  $items = $input['items'] ?? [];
Also added the missing $auth guard (consistent with all other Bring functions).

api/index.php

@@ -4672,6 +4672,13 @@ function bringGetList(): void {
 
 function bringAddItems(): void {
     $auth = bringAuth();
+    if (!$auth) {
+        echo json_encode(['success' => false, 'error' => 'Credenziali Bring! non configurate']);
+        return;
+    }
+
+    $input = json_decode(file_get_contents('php://input'), true) ?? [];
+    $items = $input['items'] ?? [];
     $listUUID = $input['listUUID'] ?? $auth['bringListUUID'];
     
     if (empty($listUUID)) {