feat: merge rustore test UI and unify SKU format across channels

- Merge VK login/link/check and Review test buttons from dev_rustore
- Unify Rustore/GooglePlay SKU format via ChannelHelpers.normalizeSkuList()
- Fix ChannelConfig runtime sync: Java InitSDK sets channel from ChannelHelpers.CHANNEL
- Fix AndroidMinSdkVersion 25→26 for tuyoosdk compatibility
- Fix Flexion AndroidManifest tools:replace missing fullBackupContent value
- Add [CHANNEL-VERIFY] debug logs for channel verification

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

sdk-intergration/Packages/tysdk/Runtime/TYSdkFacade.cs

@@ -138,6 +138,13 @@ namespace tysdk
 #endif
         }
 
+        // Called from Java SDKManager.InitSDK to sync channel
+        public void SetChannelFromNative(string ch)
+        {
+            ChannelConfig.SetChannel(ch);
+            UnityEngine.Debug.Log($"[CHANNEL-VERIFY] C# SetChannelFromNative → channel={ch}, payType={ChannelConfig.PayType}, loginTimeout={ChannelConfig.LoginTimeoutSeconds}");
+        }
+
         /*================================================
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