Expose per-product forecast errors

modules/erp/lager/forecast.php

@@ -187,7 +187,7 @@ function run_lager_stock_lot_forecast(PDO $pdo): array
     $asOfDate = new DateTimeImmutable('today', new DateTimeZone('Europe/Zurich'));
     $result = [
         'status' => 'done', 'total_products' => 0, 'processed_products' => 0,
-        'failed_products' => 0, 'failed_product_ids' => [],
+        'failed_products' => 0, 'failed_product_ids' => [], 'errors' => [],
     ];
 
     try {
@@ -208,6 +208,7 @@ function run_lager_stock_lot_forecast(PDO $pdo): array
             } catch (Throwable $error) {
                 $result['failed_products']++;
                 $result['failed_product_ids'][] = $productId;
+                $result['errors'][] = ['product_id' => $productId, 'message' => $error->getMessage()];
             }
         }
         if ($result['failed_products'] > 0) {