feat: update pricing section in user guide

- Add detailed pricing information for Reader, SERP, and DeepSeek V3
- Enhance user guide with clear token pricing structure

Author: harryisfish

content/docs/user-guide/pricing.mdx

@@ -17,6 +17,10 @@ title: Pricing
 
 后续调整请留意公告和最新充值页面。  
 
+## 定价
+1. Reader、SERP: $0.2/1M Tokens
+2. DeepSeek V3: Input $0.27/1M Tokens, Output $1.1/1M Tokens
+
 ## 用量
 暂不提供用量统计，请留意官网相应入口更新。