Racing Yacht iOS Crew App -- 2

I want a native iPhone app that keeps every aspect of my yacht’s crew administration in one place. The main flow should let me create and update the master crew list, assign people to race-day positions with simple drag-and-drop roster scheduling, and publish our racing calendar so everyone sees the latest call-times immediately.

Feature set I expect at first release
• Crew list management – add, edit, archive; searchable by name, position, or status
• Roster builder – visual calendar where I slot crew into watches or roles, with automatic notifications when something changes, crew should also be able to select races and add/delete themselves
• Racing calendar – regatta and training dates, each linked to the correct crew roster
• Crew qualifications – store certificates or licences as PDFs/photos against each profile and flag upcoming expiries
• Equipment register – record each crew-issued item with its ID number (e.g., lifejacket, PLB) and mark when it is serviced or reassigned
- app needs to be enabled with messaging for add, edits, invites, etc

Role-based access must be baked in: Admin can edit everything; crew can view and update only their own data; guests see read-only calendar and public documents.

Native iOS is mandatory so I’m thinking Swift in Xcode, but I’m open to your preferred architecture so long as it feels seamless and fast offline or in patchy marina Wi-Fi. Please outline any back-end you recommend (Firebase, Supabase, custom API, etc.) together with how you will handle secure document storage.

When replying, show me:
• A brief plan for the data model and permission layers
• Which iOS frameworks or third-party libraries you’d use
• A milestone breakdown up to App Store TestFlight delivery

Clean, maintainable code and a UI that feels at home on iOS 17 are my priorities. I’m ready to start as soon as we agree on the outline and timeline.