Users can sign in with Github OAuth on Android

[kcdragon]

Description

Opened as draft since I'm still reviewing it myself.

This PR should be reviewed in tandem with this Rails PR.

Authentication process:

1. User clicks Sign In button
2. Stimulus Bridge component intercepts the click event
3. Stimulus Bridge component sends a "signIn" message to the Native Bridge component with the OAuth authorization URL.
4. Native Bridge component launches the system browser and visits the authorization URL.
5. User fills in their credentials in the OAuth provider
6. OAuth provider calls the callback endpoint within the system browser
7. The Rails app redirects back into the Native app with the "rubyevents" custom schema and a signed token corresponding to the user
8. The Native app "replies" to the Stimulus Bridge component with the signed token
9. The Stimulus Bridge component uses Turbo to visit the "exchange" URL with the signed token and this signs in the user within the web view

Screenshots

Screen.Recording.2026-05-02.at.3.14.58.PM.mov

Testing Steps

References

• fixes Sign in to RubyEvents #6
• related to Support authenticating users with Github on native devices rubyevents#1681