Upgrade to Dart 3

**Is your feature request related to a problem? Please describe.**
Can't run the app on Dart 3 due to type safety. https://dart.dev/resources/dart-3-migration

**Describe the solution you'd like**
I would like the app migrated to Dart 3

**Describe alternatives you've considered**
I tried to migrate it myself but I am a flutter rookie and couldn't make it work.
