Chat feedback UI improvements (#68)

* feat: replace mock feedback with real API integration in FeedbackModal

* feat: integrate Markdown support in FeedbackModal and enhance feedback submission logic

* feat: implement feedback system for AI messages in ChatScreen

* feat: add course feedback retrieval and update feedback interfaces

* feat: add loading indicators for feedback and classy summary in FeedbackModal

* feat: implement feedback retrieval for students in FeedbackModal

* feat: enhance feedback screens with search functionality and improve UI elements

* feat: optimize student feedback retrieval with useMemo and improved error handling

Author: lminervino18