Hope for add support for deepseek-v4

### Before you asking

- [x] I have tried the PDFMathTranslate-next and give feedback in PDFMathTranslate-next

### Is your feature request related to a problem?

In Translate with different services function，the default model for DeepSeek is deepseek-chat which is a model without thinking. However, deepseek-v4 pro and flash has already published and in the future deepseek-chat will not be supported by DeepSeek . If we want to close think function，we must change the origin code. So we need add support for deepseek-v4 pro and flash.

### Describe the solution you'd like

According to document of DeepSeek API.
The new url is https://api.deepseek.com
The way to close thinging for both pro and flash is:

response = client.chat.completions.create(
model="deepseek-v4-pro",
# ...
extra_body={"thinking": {"type": "disabled"}}
)

### Additional context

deepseek-chat (将于 2026/07/24 弃用)
deepseek-reasoner (将于 2026/07/24 弃用)
(1) 默认思考开关为 enabled
(2) 思考模式下，对普通请求，默认 effort 为 high；对一些复杂 Agent 类请求（如 Claude Code、OpenCode），effort 自动设置为 max
(3) 思考模式下，出于兼容考虑 low、medium 会映射为 high, xhigh 会映射为 max
您在使用 OpenAI SDK 设置 thinking 参数时，需要将 thinking 参数传入 extra_body 中：
response = client.chat.completions.create(
model="deepseek-v4-pro",
# ...
reasoning_effort="high",
extra_body={"thinking": {"type": "enabled"}}
)