Add Authentication Flow WIP.

- Add Registration Screen.
- Add Server Selection Screen.
- Rename AuthenticationCoordinator to LegacyAuthenticationCoordinator.
- Add AuthenticationService and RegistrationWizard.
- Async extensions.
- Add global white and EMS colors to the themes.
- Add tests for server selection and registration screens.
- Accessibility and iPad layout tweaks.
- Remove MainActor from Auth Coordinators/VMs/Views.
(It broke the protocol conformances so now the methods and properties are marked individually.)

DesignKit/Variants/Colors/Dark/DarkColors.swift

@@ -33,6 +33,8 @@ public class DarkColors {
         tile: UIColor(rgb:0x394049),
         navigation: UIColor(rgb:0x21262C),
         background: UIColor(rgb:0x15191E),
+        white: UIColor(rgb: 0xFFFFFF),
+        ems: UIColor(rgb: 0x7E69FF),
         namesAndAvatars: [
             UIColor(rgb:0x368BD6),
             UIColor(rgb:0xAC3BA8),

DesignKit/Variants/Colors/Light/LightColors.swift

@@ -34,6 +34,8 @@ public class LightColors {
         tile: UIColor(rgb:0xF3F8FD),
         navigation: UIColor(rgb:0xF4F6FA),
         background: UIColor(rgb:0xFFFFFF),
+        white: UIColor(rgb: 0xFFFFFF),
+        ems: UIColor(rgb: 0x7E69FF),
         namesAndAvatars: [
             UIColor(rgb:0x368BD6),
             UIColor(rgb:0xAC3BA8),