Add calendar and UI updates

This update introduces a calendar for date navigation, prevents vote removals, updates the app version and icons, and refreshes UI elements including login, register screens, and themes for improved consistency.

What's New

• Date navigation now includes a calendar to select and view voting dates more easily.

• Votes cannot be removed once cast, ensuring vote integrity.

• UI elements for login, registration, and app headers have been refined for improved appearance and consistency.

Improvements

• Updated app icons and splash screen for a refreshed look.

• App version updated to 2, with version info displayed in settings.

• App themes were refreshed to improve visual consistency across screens.