refactor: missing return types, qualifier imports, code cleanup

ajax/countLang.php

ajax/getLangList.php

src/QUI/TemplateCologne/Controls/CurrencySwitch.php

src/QUI/TemplateCologne/Controls/LangCurrencySwitch.php

src/QUI/TemplateCologne/Controls/LoginAndRegister.php

src/QUI/TemplateCologne/Controls/Menu/Categories.php

src/QUI/TemplateCologne/Controls/Payments.php

src/QUI/TemplateCologne/Controls/ProductGallery.php

src/QUI/TemplateCologne/Controls/SimpleUserInfo.php

src/QUI/TemplateCologne/EventHandler.php

src/QUI/TemplateCologne/Utils.php