chore: add container, encore, redirects and upgrade tooling

Adds b13/container and ssch/typo3-encore as the base for the theme,
typo3/cms-redirects for the existing sys_redirect records and
typo3/cms-lowlevel. Rector and Fractor are configured for the
TYPO3 10 to 13 migration of the packages.

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

fractor.php

@@ -0,0 +1,17 @@
+<?php
+
+declare(strict_types=1);
+
+use a9f\Fractor\Configuration\FractorConfiguration;
+use a9f\Typo3Fractor\Set\Typo3LevelSetList;
+
+return FractorConfiguration::configure()
+    ->withPaths([
+        __DIR__ . '/packages',
+    ])
+    ->withSkip([
+        __DIR__ . '/packages/*/Resources/Private/Assets/*',
+    ])
+    ->withSets([
+        Typo3LevelSetList::UP_TO_TYPO3_13,
+    ]);