docs: add hyperlinks to sponsor images in README files (EN and CN)

README.md

@@ -8,7 +8,7 @@ It now also supports OpenAI Codex (GPT models) and Claude Code via OAuth.
 
 So you can use local or multi-account CLI access with OpenAI(include Responses)/Gemini/Claude-compatible clients and SDKs.
 
-![z.ai](asset/ad/english.png)
+[![z.ai](https://assets.router-for.me/english.png)](https://z.ai/subscribe?ic=8JVLJQFSKB)
 
 ## Sponsor
 

README_CN.md

@@ -8,7 +8,7 @@
 
 您可以使用本地或多账户的CLI方式，通过任何与 OpenAI（包括Responses）/Gemini/Claude 兼容的客户端和SDK进行访问。
 
-![bigmodel.cn](asset/ad/chinese.png)
+[![bigmodel.cn](https://assets.router-for.me/chinese.png)](https://www.bigmodel.cn/claude-code?ic=RRVJPB5SII)
 
 ## 赞助商