It does seem like you need someone on your side. A list of people to consider: your academic advisor, the professor in whose course you built the prototype application, your department chair, student ombudsman, dean of students. If the university is being as unreasonable as your posting makes it sound like, you will have no trouble getting one or more of these people on your side and they will be able to apply pressure to the registrars office on your behalf if needed to get your hold lifted.