[Dify plugin SDK] Request payload contains Unicode encoding (\uXXXX) when invoking LLM, Chinese characters not displayed correctly

source code:

<img width="1391" height="790" alt="Image" src="https://github.com/user-attachments/assets/b2b0377e-f43e-42a3-91aa-eb7ec4c7e516" />

modified code:

<img width="1440" height="715" alt="Image" src="https://github.com/user-attachments/assets/17e25ca8-16a6-408b-b5b1-657d6c849e24" />