[fix] Use vite preview port in templates for playwright config

[philip-weber]

Closes #5429 which was introduced with #5392.

I have changed the web server port from 3000 to 4173 in the playwright.config.js templates to be in line with the preview server ports from vite.

I am not totally sure if the changes to the tests are good enough. But if the vite ports will change in the future the tests should be failing.

I am also not quite sure if my selections for the changeset are correct.

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[Rich-Harris]

Thanks! A few suggestions

[philip-weber]

Thank you for your suggestions.

[Rich-Harris]

thanks!