Completed OIDC Authorization Code Flow with PKCE (S256) for JS and JVM platforms.
- Added `launchOidcFlow`, `consumePendingOidcCallback`, and `getOidcRedirectUri` with platform-specific implementations.
- Integrated SHA-256 and Base64URL helpers for PKCE.
- Updated `LoginViewModel` with OIDC logic (key handling, token exchange, state validation).
- Enhanced `LoginScreen` with an OIDC login button and loading spinner.
- Verified implementation with system hardening roadmap tasks.
Includes browser redirects for JS, localhost HTTP callback for JVM, and built-in Keycloak URL construction.
Signed-off-by: Stefan Mogeritsch <stefan.mo.co@gmail.com>
Stefan Mogeritsch
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