[Task]: Fix splash screen delays

[cvarley100]

Task description

On both Android and iOS the splash screen behaviour could be improved. On app open, the splash screen should display until the login screen is ready to render.

Requirements

There should be no gap between the splash screen closing and login screen rendering.

Creation checklist

• [X] I have assigned this task to the correct people
• [X] I have added the most appropriate labels
• [X] I have linked the correct milestone and/or project