Added second onboarding screen with avatar selection for better user experience

Added In-App-Purchases

- Users can now choose whether they are represented as male or female in the human chain visualization.
- An optional account linking feature was added (email and password) to allow users to securely save and restore their position in the chain across devices.
- Users can optionally personalize their avatar with additional colors via in-app purchases.
- Minor user interface and usability improvements.

What's new in 1.0.1:

  • Dark mode: Choose between light, dark, or follow your system theme
  • Stats section: See which countries have the most people in the chain
  • Review prompt: Help spread the word by leaving a review with your country