refactor: update code base to php 8 and set phpstan lvl to 6

app/Libraries/Negotiate.php

app/Libraries/Router.php

app/Models/ActorModel.php

app/Models/CategoryModel.php

app/Models/EpisodeModel.php

app/Models/EpisodePersonModel.php

app/Models/LanguageModel.php

app/Models/NoteModel.php

app/Models/PageModel.php

app/Models/PersonModel.php

app/Models/PlatformModel.php

app/Models/PodcastModel.php

app/Models/PodcastPersonModel.php

app/Models/SoundbiteModel.php

app/Models/UserModel.php

app/Validation/FileRules.php

app/Views/errors/cli/error_exception.php

composer.json

composer.lock

phpstan.neon