Motivation

• Provide deterministic, testable biometric behavior for sign-in and settings so host and JVM UI tests can exercise success, cancellation, hard-failure and fallback flows.
• Ensure the settings screen can represent and toggle biometric availability and enablement state so lifecycle and unsupported-device cases are covered.
• Surface a biometric action and UI affordance on the sign-in screen to validate visibility and UX-preservation when biometric is unavailable.

Description

• Add BiometricAuthenticator and BiometricAuthResult to presentation.signin and wire a OnBiometricSignInClick action into SignInViewModel with signInWithBiometric() handling success, cancel and error paths, and exposing isBiometricAvailable for the UI.
• Add BiometricSettingsGateway and integrate it into SettingsViewModel with a ToggleBiometric action and biometricSupported/biometricEnabled fields on SettingsResult for state propagation.
• Add a biometric button and test tag (SIGN_IN_BIOMETRIC_BUTTON_TAG) to the sign-in UI (SignInScreen) and update shared Koin modules to provide no-op implementations so existing app wiring stays functional without platform biometric implementations.
• Add tests colocated with existing suites: host tests in core/presentation/src/androidHostTest (SignInViewModelTest, SettingsViewModelTest) covering biometric success/cancel/error/fallback and settings enable/disable/unsupported-device behavior, and a JVM Compose UI test in core/ui/src/jvmTest (SignInScreenBiometricTest) covering biometric button visibility and fallback UX preservation.

Testing

• Added the following automated tests (not executed to completion in this environment): SignInViewModelTest (biometric success/cancel/error/fallback), SettingsViewModelTest (biometric enable/disable lifecycle and unsupported-device behavior), and SignInScreenBiometricTest (UI visibility and password UX preservation).
• Attempted to run ./gradlew :core:presentation:androidHostTest :core:ui:jvmTest --no-daemon but the build failed in this environment due to a plugin resolution error for org.gradle.kotlin.kotlin-dsl (plugin artifact could not be resolved), so tests were not run here.
• All new tests are colocated with existing suites under core/presentation/src/androidHostTest and core/ui/src/jvmTest so they will run in CI or a developer environment where Gradle can resolve plugins and device/emulator requirements are met.

Codex Task