Simplify PasscodeManager API and decouple passcode/biometrics libraries (#73)

* Refactor biometric authentication logic into a generalized external authentication framework.

*   Rename all biometric-related references to "ExternalAuth" across `PasscodeManager`, `PasscodeScreen`, and associated components to support a broader range of authentication methods.
*   Introduce `BiometricStorageAdapter` interface and implementation to decouple biometric registration data from the core passcode module.
*   Deprecate registration-related methods in `PasscodeStorageAdapter` in favor of the new `BiometricStorageAdapter`.
*   Update `PasscodeManager` initialization and `PasscodeState` to use `isExternalAuthEnabled` instead of specific biometric flags.
*   Rename `PasscodeAction` and `PasscodeEvent` cases, such as `BiometricUnlockSuccess` to `ExternalUnlockSuccess` and `DisableBiometrics` to `DisableExternalAuth`.
*   Update `PasscodeScreen` and `PasscodeKeys` to use `externalAuthButton` as a generic slot for platform-specific authentication triggers.
*   Refactor navigation and setup logic in the sample app to integrate the new storage adapters and renamed callbacks.
*   Update string resource keys to reflect the transition from biometric-specific naming to external authentication.

* Refactor `PasscodeManager` and `PasscodeScreen` to use a direct method API and a unified result callback.

*   **Passcode Logic and State Management**:
    *   Refactor `PasscodeManager` to remove `CoroutineScope` and internal `Action`/`Event` channels, replacing them with direct method calls (e.g., `enterKey`, `changePasscode`, `logOut`).
    *   Introduce `PasscodeResult` sealed interface to consolidate all operation outcomes (Verified, Created, Changed, etc.) into a single callback.
    *   Add `shakeAnimationTrigger` to `PasscodeState` to handle UI feedback for rejected passcodes without relying on one-shot events.
    *   Simplify `PasscodeManager` initialization by passing `isExternalAuthEnabled` directly to the constructor.

*   **UI Components**:
    *   Update `PasscodeScreen` to use a single `onResult` lambda instead of multiple individual event callbacks.
    *   Replace `LaunchedEffect` event collection with a `DisposableEffect` that registers the result callback.
    *   Rename `biometricButton` to `externalAuthButton` in `PasscodeScreen` to be more agnostic of the authentication mechanism.
    *   Update `PasscodeKeys`, `PasscodeLengthSwitch`, and `PasscodeForgotButton` to invoke manager methods directly.

*   **Integration and Navigation**:
    *   Update `SampleAppNavigation` to map `PasscodeResult` values to navigation routes and storage updates.
    *   Refactor `BiometricKey` and `BiometricSetupScreen` to interact with the updated `PasscodeManager` API, manually handling external auth status updates.
    *   Update `BiometricStorageAdapter` implementation to separate biometric persistence from passcode persistence.

*   **Documentation and API**:
    *   Update `README.md` for both passcode and biometrics modules to reflect the new API patterns and integration steps.
    *   Add `UserCancelled` state to `RegistrationResult` and `AuthenticationResult` in the biometrics module.
    *   Refine `PasscodeStorageAdapter` interface to focus exclusively on passcode data.

* Refactor sample app navigation and modularize screen components.

* Extract `HomeScreen`, `LoginScreen`, and `BiometricKey` into dedicated files within the `cmp-sample-shared` module to improve project structure.
* Update `SampleAppNavigation` to handle consolidated `PasscodeResult` events, including verified, created, changed, and forgotten states.
* Ensure consistent backstack management by using `popUpTo(0)` when navigating to top-level screens like `HomeScreen` and `LoginScreen`.
* Update `PasscodeManager` to fully reset the internal state, including `isChangeFlow` and `isExternalAuthEnabled` flags, when clearing all security data.
* Remove the redundant `SettingsPasscodeScreen` route.
* Enhance `HomeScreen` with logic for toggling biometric authentication and triggering the passcode change flow.
* Refactor `BiometricKey` to handle biometric authentication results and provide appropriate user feedback via callbacks.

Author: TheKalpeshPawar

cmp-sample-shared/src/commonMain/kotlin/cmp/sample/shared/BiometricStorageAdapterImpl.kt

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2026 Mifos Initiative
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See https://github.com/openMF/mifos-passcode-cmp/blob/development/LICENSE
+ */
+package cmp.sample.shared
+
+import com.russhwolf.settings.Settings
+import org.mifos.authenticator.biometrics.BiometricStorageAdapter
+
+private const val REGISTRATION_DATA_KEY = "org.mifos.authenticator.registration_data"
+
+class BiometricStorageAdapterImpl(
+    private val settings: Settings,
+) : BiometricStorageAdapter {
+    override fun saveRegistrationData(registrationData: String) {
+        settings.putString(REGISTRATION_DATA_KEY, registrationData)
+    }
+
+    override fun loadRegistrationData(): String? {
+        return settings.getStringOrNull(REGISTRATION_DATA_KEY)
+    }
+
+    override fun deleteRegistrationData() {
+        settings.remove(REGISTRATION_DATA_KEY)
+    }
+}

cmp-sample-shared/src/commonMain/kotlin/cmp/sample/shared/PasscodeStorageAdapterImpl.kt

@@ -12,8 +12,7 @@ package cmp.sample.shared
 import com.russhwolf.settings.Settings
 import org.mifos.authenticator.passcode.PasscodeStorageAdapter
 
-const val PASSCODE_KEY = "org.mifos.authenticator.passcode"
-const val REGISTRATION_DATA_KEY = "org.mifos.authenticator.registration_data"
+private const val PASSCODE_KEY = "org.mifos.authenticator.passcode"
 
 class PasscodeStorageAdapterImpl(
     private val settings: Settings,
@@ -30,15 +29,12 @@ class PasscodeStorageAdapterImpl(
         settings.remove(PASSCODE_KEY)
     }
 
-    override fun saveRegistrationData(registrationData: String) {
-        settings.putString(REGISTRATION_DATA_KEY, registrationData)
-    }
+    @Suppress("DEPRECATION")
+    override fun saveRegistrationData(registrationData: String) { }
 
-    override fun loadRegistrationData(): String? {
-        return settings.getStringOrNull(REGISTRATION_DATA_KEY)
-    }
+    @Suppress("DEPRECATION")
+    override fun loadRegistrationData(): String? = null
 
-    override fun deleteRegistrationData() {
-        settings.remove(REGISTRATION_DATA_KEY)
-    }
+    @Suppress("DEPRECATION")
+    override fun deleteRegistrationData() { }
 }

cmp-sample-shared/src/commonMain/kotlin/cmp/sample/shared/di/PasscodeModule.kt

@@ -9,21 +9,25 @@
  */
 package cmp.sample.shared.di
 
+import cmp.sample.shared.BiometricStorageAdapterImpl
 import cmp.sample.shared.PasscodeStorageAdapterImpl
 import com.russhwolf.settings.Settings
-import kotlinx.coroutines.MainScope
 import org.koin.core.context.startKoin
 import org.koin.core.module.dsl.singleOf
 import org.koin.dsl.KoinAppDeclaration
 import org.koin.dsl.bind
 import org.koin.dsl.module
+import org.mifos.authenticator.biometrics.BiometricStorageAdapter
 import org.mifos.authenticator.passcode.PasscodeManager
 import org.mifos.authenticator.passcode.PasscodeStorageAdapter
 
 val passcodeModule = module {
     singleOf(::PasscodeStorageAdapterImpl).bind<PasscodeStorageAdapter>()
+    singleOf(::BiometricStorageAdapterImpl).bind<BiometricStorageAdapter>()
     single {
-        PasscodeManager(get(), MainScope()).initialize()
+        val biometricAdapter = get<BiometricStorageAdapter>()
+        val isExternalAuthEnabled = biometricAdapter.loadRegistrationData() != null
+        PasscodeManager(get(), isExternalAuthEnabled)
     }
     single { Settings() }
 }

cmp-sample-shared/src/commonMain/kotlin/cmp/sample/shared/navigation/Route.kt

@@ -23,7 +23,4 @@ sealed class Route {
 
     @Serializable
     data object BiometricSetupScreen : Route()
-
-    @Serializable
-    data object SettingsPasscodeScreen : Route()
 }