feat: Flexion channel build fixes

- Add google-services.json per-channel copy in SwitchChannel (Flexion has extra client)
- Add GooglePlay default google-services.json for fallback
- Switch Bundle Identifier per channel (Flexion → com.arkgame.ft.flexion)
- Fix FlexionSDKHelper missing BillingService import
- Fix Flexion AndroidManifest: add fullBackupContent override with flexion_backup_rules
- Add MainProcessName tools:replace to resolve gasdk/tuyoosdk manifest conflict
- Add billing:6.0.1 dependency for tuyoosdk AAR init compatibility

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

sdk-intergration/Assets/Editor/ChannelBuildTool.cs

@@ -9,6 +9,7 @@ public class ChannelBuildTool
 
     private const string ExtraCfgRoot = "../ExtraPluginCfgs/Android";
     private const string TysdkPlugins = "Packages/tysdk/Plugins/Android";
+    private const string TysdkFiles = "Packages/tysdk/Files";
     private const string AssetsPlugins = "Assets/Plugins/Android";
 
     private static readonly string[] GradleFiles =
@@ -78,7 +79,24 @@ public class ChannelBuildTool
             Debug.Log($"[ChannelSwitch] Java: {javaFile} → {dest}");
         }
 
-        // 5. Set runtime channel
+        // 5. Sync google-services.json (fallback to GooglePlay default)
+        var srcGoogleServices = Path.Combine(cfgDir, "Files/google-services.json");
+        if (!File.Exists(srcGoogleServices))
+            srcGoogleServices = Path.Combine(ExtraCfgRoot, "googleplay/Files/google-services.json");
+        var destGoogleServices = Path.Combine(TysdkFiles, "google-services.json");
+        File.Copy(srcGoogleServices, destGoogleServices, true);
+        Debug.Log($"[ChannelSwitch] google-services.json: {srcGoogleServices} → {destGoogleServices}");
+
+        // 6. Set Bundle Identifier per channel
+        var bundleId = channel switch
+        {
+            "Flexion" => "com.arkgame.ft.flexion",
+            _ => "com.arkgame.ft"
+        };
+        PlayerSettings.SetApplicationIdentifier(BuildTargetGroup.Android, bundleId);
+        Debug.Log($"[CHANNEL-VERIFY] Bundle Identifier → {bundleId}");
+
+        // 7. Set runtime channel
         tysdk.ChannelConfig.SetChannel(channel);
 
         AssetDatabase.Refresh(ImportAssetOptions.ForceSynchronousImport);