feat: report the source export timestamp on every travel export page

src/Service/TravelExportBuilder.php

@@ -6,6 +6,7 @@ namespace App\Service;
 
 use App\BusProNet\Model\Hotel;
 use App\BusProNet\Model\Pickup;
+use App\BusProNet\Model\XmlExportInfo;
 use App\BusProNet\Traits\TypeConversionTrait;
 use App\BusProNet\XmlCrawlerFactory;
 use App\BusProNet\XmlLoader\HotelLoader;
@@ -67,6 +68,11 @@ class TravelExportBuilder
 
     private function assemble(): TravelExport
     {
+        // Read before the walk and cached with the rows, so every page served from this
+        // copy names the same source export. A client that sees it change between pages
+        // knows xml-sync swapped the export underneath its walk.
+        $sourceGeneratedAt = XmlExportInfo::fromStorage($this->xmlExport)?->lastTransfer;
+
         $hotels = $this->hotelLoader->loadAll();
         $pickupMasterData = $this->pickupLoader->loadAll();
 
@@ -96,6 +102,7 @@ class TravelExportBuilder
             $skipped,
             count($pickupsWithoutMasterData),
             new \DateTimeImmutable(),
+            $sourceGeneratedAt,
         );
     }