muddassir1718/AgeVault — reverse-engineered prompt

Build me AgeVault 2026, a polished birthday and age tracking web app that feels modern, personal, and fun.

I want users to enter their birth date and instantly see their exact age in years, months, days, hours, minutes, and seconds, updating live. Also show interesting life facts like estimated heartbeats, sleep time, and sun or moon related cycles in a friendly way. Add a birthday vault where people can save family and friends birthdays, keep them after refresh, see countdowns, and generate nice greeting messages when a birthday is coming.

Please make it fully responsive for mobile and desktop, and make the core calculations work in the browser without needing a backend so it can run offline. Include beautiful theme options like Cosmic, Sakura, Aurora, Solar, and Slate, plus a custom color picker. The app should feel smooth with nice animations, but still be easy for normal people to use.

Use the existing project setup and look up current docs online if needed.