refs #21064 [fid] fix code style

* devops info:
** run "./install-codestylechecker.sh install" to install dependencies for git hooks code style checks
** see https://projekte.ub.uni-leipzig.de/projects/finc-intern/wiki/Code-Quality-Checking_mit_PHPStorm#section-5 for integration of CS Fixer validation in PHPStorm
* $HOME/bin/codestylechecker/php-cs-fixer3 fix --config=$HOME/bin/codestylechecker/vufind.php-cs-fixer.php_cs module/fid/src/
* add missing class and method comments
* move view helper classes to correct directory
* run codesniffer-beautifier for modules and templates

co-authored by: Dorian Merz <merz@ub.uni-leipzig.de>
co-authored by: Alexander Purr <purr@ub.uni-leipzig.de>