Product text import from agency XLSX workbooks

VITEC Import module: Products tab is now a searchable/sortable product
overview. "Edit Product" opens an XLSX upload with per-field source
mapping (component + cell), old/new preview and checkbox apply via
DataHandler; the mapping and manual matches are persisted and preselect
the next workbook. Category workbooks are detected and rejected.

- new: ProductXlsxReader (PhpSpreadsheet), ProductTextImportController,
  Products/ProductTexts templates, 4 module routes
- related products: per-pair card text in new side table
  tx_vitec_product_related_text (survives MM rewrites), emitted as
  `cardtext` in the product JSON; missing MM relations added add-only
- card copy read from Body Copy (D) with fallback to CTA/Card Copy (E) -
  the workbooks fill either depending on row type
- product detail page <title> now uses seotitle with title fallback
  (provider made singleton and fed from the JSON renderer)
- per-user recent-search badges; last loaded workbook stored per product
  (tx_vitec_product_workbook), Edit Product reopens on it
- composer: add phpoffice/phpspreadsheet ^5.9
- diagnostics: migrations/check_workbook.php

packages/vitec/Classes/PageTitle/ProductPageTitleProvider.php

@@ -5,8 +5,16 @@ declare(strict_types=1);
 namespace Evomedien\Vitec\PageTitle;
 
 use TYPO3\CMS\Core\PageTitle\AbstractPageTitleProvider;
+use TYPO3\CMS\Core\SingletonInterface;
 
-final class ProductPageTitleProvider extends AbstractPageTitleProvider
+/**
+ * Singleton on purpose: whoever sets the title (ProductShowJsonRenderer in
+ * headless mode, ProductController in classic mode) and the
+ * PageTitleProviderManager that later reads it both obtain the provider via
+ * GeneralUtility::makeInstance(). Without the singleton those are two
+ * different instances and the title set here is never seen by the manager.
+ */
+final class ProductPageTitleProvider extends AbstractPageTitleProvider implements SingletonInterface
 {
 private string $seotitle = '';