build(android): integrate Google Services plugin for Firebase support

Add Google Services Gradle plugin integration to withHuaweiPush.js to enable Firebase initialization alongside Huawei Push. This includes:
- Adding google-services classpath dependency for buildscript
- Applying com.google.gms.google-services plugin after React plugin
- Copying google-services.json to android/app/ for runtime initialization

Without these changes, Firebase initialization fails at runtime with "default FirebaseApp is not initialized" when google-services.json is configured in app.json.

plugins/withHuaweiPush.js

@@ -97,6 +97,17 @@ const withHuaweiPush = (config, options = {}) => {
       );
     }
 
+    // Google Services plugin classpath — required for Firebase init via google-services.json.
+    if (!contents.includes('com.google.gms:google-services')) {
+      const depsPattern = /(buildscript\s*\{[\s\S]*?dependencies\s*\{[\s\S]*?classpath\(['"]org\.jetbrains\.kotlin:kotlin-gradle-plugin['"]\))/;
+      if (depsPattern.test(config.modResults.contents)) {
+        config.modResults.contents = config.modResults.contents.replace(
+          depsPattern,
+          `$1\n    classpath('com.google.gms:google-services:4.4.4')`
+        );
+      }
+    }
+
     if (!config.modResults.contents.includes('developer.huawei.com/repo')) {
       const bsRepoPattern = /(buildscript\s*\{[\s\S]*?repositories\s*\{)/;
       if (bsRepoPattern.test(config.modResults.contents)) {
@@ -113,6 +124,22 @@ const withHuaweiPush = (config, options = {}) => {
   config = withAppBuildGradle(config, (config) => {
     const contents = config.modResults.contents;
 
+    // Apply Google Services plugin (Firebase) before the Huawei plugin.
+    // The googleServicesFile in app.json only sets up the file copy + plugin
+    // when run through `expo prebuild`, but it does not coexist with this
+    // Huawei plugin reliably, so we apply it explicitly here.
+    if (!contents.includes('com.google.gms.google-services')) {
+      const reactApply = /apply plugin:\s*['"]com\.facebook\.react['"]\s*\n/;
+      if (reactApply.test(contents)) {
+        config.modResults.contents = contents.replace(
+          reactApply,
+          `apply plugin: "com.facebook.react"\napply plugin: 'com.google.gms.google-services'\n`
+        );
+      } else {
+        config.modResults.contents = `apply plugin: 'com.google.gms.google-services'\n` + contents;
+      }
+    }
+
     if (!contents.includes('com.huawei.agconnect')) {
       const applyPluginPattern = /apply plugin:\s*['"]com\.google\.gms\.google-services['"]/;
       if (applyPluginPattern.test(contents)) {
@@ -163,6 +190,18 @@ const withHuaweiPush = (config, options = {}) => {
         console.warn('[withHuaweiPush] agconnect-services.json not found at project root');
       }
 
+      // Copy google-services.json to android/app/ so the Google Services
+      // Gradle plugin can find it. Without this, FCM / Firebase init fails
+      // at runtime with "default FirebaseApp is not initialized".
+      const gmsSrc = path.join(config.modRequest.projectRoot, 'google-services.json');
+      const gmsDest = path.join(appDir, 'google-services.json');
+      if (fs.existsSync(gmsSrc)) {
+        fs.copyFileSync(gmsSrc, gmsDest);
+        console.log('[withHuaweiPush] copied google-services.json to android/app/');
+      } else {
+        console.warn('[withHuaweiPush] google-services.json not found at project root');
+      }
+
       // RN 0.85.3 ships Gradle 9.3.1 in its template, but Kotlin 2.1.20 is incompatible
       // with Gradle 9.x (CompilerEnvironment ClassNotFoundException). Downgrade to 8.14.5.
       const wrapperFile = path.join(config.modRequest.platformProjectRoot, 'gradle', 'wrapper', 'gradle-wrapper.properties');