refactor: PHP 8.5 language features via Rector

rector.php gets the PHP sets up to 8.5. Mostly constructor promotion with
readonly properties, typed class constants, ??=, arrow functions,
str_contains/str_starts_with, catch without unused variables, array_any
and #[\Override] on overridden properties; array_key_exists() keys are
cast to string (null keys are deprecated in PHP 8.5). Long promoted
constructor signatures are wrapped one parameter per line.

Checked locally: a crawl of ~1,900 frontend URLs over all sites and the
backchannel APIs (/api/hotel, /api/product, content feed manifest and
records of every type) render the same as before.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/ep_theme/Configuration/TCA/Overrides/tt_content_element_container.php

@@ -55,7 +55,7 @@ call_user_func(function () {
             $row[] = $config;
         }
         GeneralUtility::makeInstance(Registry::class)->configureContainer(
-            (new ContainerConfiguration($cType, $label, $description, [$row]))
+            new ContainerConfiguration($cType, $label, $description, [$row])
                 ->setIcon('tx_eptheme_gridelements_' . $icon)
         );
     }

packages/ep_theme/Configuration/TCA/tx_eptheme_domain_model_lineup.php

@@ -113,7 +113,8 @@ return [
 			'config' => [
 				'type' => 'input',
 				'size' => 30,
-				'eval' => 'trim,required'
+				'eval' => 'trim',
+                'required' => true
 			],
 		],
         'description' => [