[TASK] Add `return` statement to all `redirect()`

[rintisch]

All redirect() calls need to be "prefixed" with return in TYPO3 v12 to work properly, see https://docs.typo3.org/c/typo3/cms-core/main/en-us/Changelog/11.3/Deprecation-94351-ExtextbaseStopActionException.html

Fixes #483