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/Plugins/Android/settingsTemplate.gradle

@@ -18,9 +18,6 @@ dependencyResolutionManagement {
         mavenCentral()
 // Android Resolver Repos Start
         def unityProjectPath = $/file:///**DIR_UNITYPROJECT**/$.replace("\\", "/")
-        maven {
-            url "https://sdk.tapjoy.com/" // Packages/com.unity.package-offerwall/Editor/TJPluginDependencies.xml:9
-        }
         maven {
             url "https://android-sdk.is.com/" // Assets/MaxSdk/Mediation/IronSource/Editor/Dependencies.xml:8
         }