tutao/tutanota — reverse-engineered prompt

Build me a secure email app like Tuta Mail. I want people to be able to sign in, send and receive private email, manage contacts, and use a calendar, with encryption built in so privacy is the main point rather than an extra setting.

It should work as a web app first, but please structure it so desktop and mobile clients could share as much code as possible later. Keep the interface clean and simple, with inbox, compose, contacts, calendar, settings, and clear messages when something is encrypted or needs attention.

Please include the core flows, account setup, login, mailbox view, reading and composing mail, contact management, calendar entries, and basic security settings. Use TypeScript and a modern frontend approach. If you need details on encryption or platform setup, look up current docs online and make sensible choices.