docs: README 顶部互加语言切换链接，文档站仅保留中文 README 跳转

- README.md 顶部加 '中文 | English' 语言切换，链接至 README.zh-Hans.md
- README.zh-Hans.md 顶部加 '中文 | English' 语言切换，链接至 README.md
- website/docs/intro.md：移除重复中文内容，改为 info admonition 链接至 GitHub 中文 README

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Slartbartfast1

README.md

@@ -1,3 +1,5 @@
+**[中文](README.zh-Hans.md)** | English
+
 <div align="center">
 
 # Quant Flow

README.zh-Hans.md

@@ -1,3 +1,5 @@
+中文 | **[English](README.md)**
+
 <div align="center">
 
 # Quant Flow

website/docs/intro.md

@@ -4,6 +4,10 @@ title: Introduction
 description: Quant Flow — AI-powered crypto perpetual futures trading bot for Hyperliquid DEX
 ---
 
+:::info 中文文档
+查看 GitHub 上的中文说明：[README.zh-Hans.md](https://github.com/loadchange/quant-flow/blob/main/README.zh-Hans.md)
+:::
+
 # Quant Flow
 
 **Quant Flow** is an AI-powered cryptocurrency trading system built on [LangChain](https://langchain.com/) / [LangGraph](https://langchain-ai.github.io/langgraph/) for the [Hyperliquid DEX](https://hyperliquid.xyz/). It combines large language models with quantitative trading logic to make autonomous trading decisions on perpetual futures markets.