docs: clarify Chinese README license label

The LICENSE file adds commercial restrictions on top of Apache 2.0, so the
README should not advertise the project as plain "Apache 2.0". Match the
actual terms.

Closes #3144

Co-authored-by: multica-agent <github@multica.ai>

README.zh-CN.md

@@ -176,4 +176,4 @@ iOS 移动端代码位于 [`apps/mobile/`](apps/mobile/)，自己编译装到手
 
 ## 开源协议
 
-[Apache 2.0](LICENSE)
+[Modified Apache 2.0 (with commercial restrictions)](LICENSE)