Work Permit?/Temporary stay? - UK national (Zagreb)

Hi All,
I have been offered a job in Hvar this summer- Protected content
Really looking forward to it, but I have some questions about the work permit system and what is required for a UK national

I have a UK & Australian passport, and understand I can only remain in Croatia for 90 days without a work permit or a stay and work permit.

My potential employer has suggested a internship? as I won't need a permit then? Another option is self employment?

I have received a job description and contract.

I am a bit lost, so if anyone has some advice on where to go on the web or even personal experience, much appreciated.

Dave