Add listener API to OverrideColorScheme for dynamic dark mode updates (facebook#54791)

Summary:
Pull Request resolved: facebook#54791

This change adds a listener mechanism to the `OverrideColorScheme` interface to enable dynamic updates when the user's dark mode preference changes via `OverrideColorScheme`.

Previously, `AppearanceModule` would only reflect the initial color scheme state when instantiated. If a user toggled dark mode through an `OverrideColorScheme` implementation, React Native JavaScript would not be notified of the change, causing UI inconsistencies.

This implementation adds:
1. An optional `addSchemeChangeListener()` method to the `OverrideColorScheme` interface with a default no-op implementation for backward compatibility. Also adding matching `removeSchemeChangeListener()`.
2. Automatic listener registration in `AppearanceModule`'s init block that triggers `onConfigurationChanged()` when the color scheme changes

Changelog:
[Android][Added] - Add `{add|remove}SchemeChangeListener()` function to `OverrideColorScheme` interface to support dynamic appearance updates via override

Reviewed By: javache

Differential Revision: D88427482

fbshipit-source-id: 02b71335bb5bebd1f44bf9723c3120f9a1fc182c

Author: alanleedev

packages/react-native/ReactAndroid/api/ReactAndroid.api

@@ -2465,6 +2465,7 @@ public final class com/facebook/react/modules/appearance/AppearanceModule : com/
 	public fun addListener (Ljava/lang/String;)V
 	public final fun emitAppearanceChanged (Ljava/lang/String;)V
 	public fun getColorScheme ()Ljava/lang/String;
+	public fun invalidate ()V
 	public final fun invalidatePlatformColorCache ()V
 	public final fun onConfigurationChanged (Landroid/content/Context;)V
 	public fun removeListeners (D)V
@@ -2475,7 +2476,14 @@ public final class com/facebook/react/modules/appearance/AppearanceModule$Compan
 }
 
 public abstract interface class com/facebook/react/modules/appearance/AppearanceModule$OverrideColorScheme {
+	public abstract fun addSchemeChangeListener (Lkotlin/jvm/functions/Function0;)V
 	public abstract fun getScheme ()Ljava/lang/String;
+	public abstract fun removeSchemeChangeListener (Lkotlin/jvm/functions/Function0;)V
+}
+
+public final class com/facebook/react/modules/appearance/AppearanceModule$OverrideColorScheme$DefaultImpls {
+	public static fun addSchemeChangeListener (Lcom/facebook/react/modules/appearance/AppearanceModule$OverrideColorScheme;Lkotlin/jvm/functions/Function0;)V
+	public static fun removeSchemeChangeListener (Lcom/facebook/react/modules/appearance/AppearanceModule$OverrideColorScheme;Lkotlin/jvm/functions/Function0;)V
 }
 
 public abstract interface class com/facebook/react/modules/appregistry/AppRegistry : com/facebook/react/bridge/JavaScriptModule {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/modules/appearance/AppearanceModule.kt

@@ -28,13 +28,42 @@ constructor(
 
   private var lastEmittedColorScheme: String? = null
 
+  private val schemeChangeListener: () -> Unit = {
+    val activity = reactApplicationContext.getCurrentActivity()
+    onConfigurationChanged(activity ?: reactApplicationContext)
+  }
+
+  init {
+    // Register as a listener for color scheme changes if override is provided
+    overrideColorScheme?.addSchemeChangeListener(schemeChangeListener)
+  }
+
   /** Optional override to the current color scheme */
-  public fun interface OverrideColorScheme {
+  public interface OverrideColorScheme {
     /**
      * Color scheme will use the return value instead of the current system configuration. Available
      * scheme: {light, dark}
      */
     public fun getScheme(): String
+
+    /**
+     * Register a listener to be notified when the color scheme changes. The listener will be
+     * invoked whenever the underlying theme preference changes.
+     *
+     * Default implementation does nothing. Override this method if you want to support dynamic
+     * color scheme updates.
+     */
+    public fun addSchemeChangeListener(listener: () -> Unit) {
+      // no-op
+    }
+
+    /**
+     * Unregisters a previously added color scheme change listener. Default implementation is a
+     * no-op; override to remove the listener from your source.
+     */
+    public fun removeSchemeChangeListener(listener: () -> Unit) {
+      // no-op
+    }
   }
 
   private fun colorSchemeForCurrentConfiguration(context: Context): String {
@@ -98,6 +127,12 @@ constructor(
     Companion.invalidatePlatformColorCache?.run()
   }
 
+  public override fun invalidate() {
+    overrideColorScheme?.removeSchemeChangeListener(schemeChangeListener)
+    invalidatePlatformColorCache()
+    super.invalidate()
+  }
+
   public companion object {
     public const val NAME: String = NativeAppearanceSpec.NAME
     private const val APPEARANCE_CHANGED_EVENT_NAME = "appearanceChanged"