refactor: convert AppOpenAdPlugin and AppOpenAdManager from Java to Kotlin

Convert both App Open Ad files to idiomatic Kotlin per reviewer request.
Uses Kotlin features: named parameters, apply blocks, null safety,
fun interface, property accessors, and lambda syntax.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: 2 people

android/src/main/java/com/getcapacitor/community/admob/appopen/AppOpenAdManager.java

@@ -0,0 +1,86 @@
+package com.getcapacitor.community.admob.appopen
+
+import android.app.Activity
+import android.content.Context
+import com.google.android.gms.ads.AdError
+import com.google.android.gms.ads.AdRequest
+import com.google.android.gms.ads.FullScreenContentCallback
+import com.google.android.gms.ads.LoadAdError
+import com.google.android.gms.ads.appopen.AppOpenAd
+
+class AppOpenAdManager(val adUnitId: String) {
+
+    private var appOpenAd: AppOpenAd? = null
+    private var isLoadingAd = false
+    private var isShowingAd = false
+
+    val isAdLoaded: Boolean
+        get() = appOpenAd != null
+
+    fun loadAd(context: Context, onLoaded: () -> Unit, onFailed: (LoadAdError?) -> Unit) {
+        if (appOpenAd != null) {
+            onLoaded()
+            return
+        }
+
+        if (isLoadingAd) {
+            onFailed(null)
+            return
+        }
+
+        isLoadingAd = true
+        val request = AdRequest.Builder().build()
+
+        // play-services-ads 24.x: orientation overload removed; SDK picks orientation from the activity.
+        AppOpenAd.load(
+            context,
+            adUnitId,
+            request,
+            object : AppOpenAd.AppOpenAdLoadCallback() {
+                override fun onAdLoaded(ad: AppOpenAd) {
+                    appOpenAd = ad
+                    isLoadingAd = false
+                    onLoaded()
+                }
+
+                override fun onAdFailedToLoad(loadAdError: LoadAdError) {
+                    isLoadingAd = false
+                    onFailed(loadAdError)
+                }
+            }
+        )
+    }
+
+    fun showAdIfAvailable(
+        activity: Activity,
+        onOpened: () -> Unit,
+        onClosed: () -> Unit,
+        onFailedToShow: (AdError?) -> Unit
+    ) {
+        if (appOpenAd == null || isShowingAd) {
+            onFailedToShow(null)
+            return
+        }
+
+        isShowingAd = true
+        appOpenAd?.fullScreenContentCallback = object : FullScreenContentCallback() {
+            override fun onAdShowedFullScreenContent() {
+                onOpened()
+            }
+
+            override fun onAdDismissedFullScreenContent() {
+                appOpenAd = null
+                isShowingAd = false
+                onClosed()
+            }
+
+            override fun onAdFailedToShowFullScreenContent(adError: AdError) {
+                appOpenAd = null
+                isShowingAd = false
+                onFailedToShow(adError)
+            }
+        }
+
+        appOpenAd?.show(activity)
+    }
+}