docs: add iframe integration feature and ecosystem projects section

README.md

@@ -39,6 +39,15 @@ Sub2API is an AI API gateway platform designed to distribute and manage API quot
 - **Concurrency Control** - Per-user and per-account concurrency limits
 - **Rate Limiting** - Configurable request and token rate limits
 - **Admin Dashboard** - Web interface for monitoring and management
+- **External System Integration** - Embed external systems (e.g. payment, ticketing) via iframe to extend the admin dashboard
+
+## Ecosystem
+
+Sub2API supports embedding external systems via iframe to extend the admin dashboard. Here are community-recommended integration projects:
+
+| Project | Description | Features |
+|---------|-------------|----------|
+| [Sub2ApiPay](https://github.com/touwaeriol/sub2apipay) | Self-service payment system | Self-service top-up and subscription purchase; supports YiPay protocol, WeChat Pay, Alipay, Stripe |
 
 ## Tech Stack
 

README_CN.md

@@ -39,6 +39,15 @@ Sub2API 是一个 AI API 网关平台，用于分发和管理 AI 产品订阅（
 - **并发控制** - 用户级和账号级并发限制
 - **速率限制** - 可配置的请求和 Token 速率限制
 - **管理后台** - Web 界面进行监控和管理
+- **外部系统集成** - 支持通过 iframe 嵌入外部系统（如支付、工单等），扩展管理后台功能
+
+## 生态项目
+
+Sub2API 支持通过 iframe 嵌入外部系统，扩展管理后台功能。以下是社区推荐的集成项目：
+
+| 项目 | 说明 | 功能 |
+|------|------|------|
+| [Sub2ApiPay](https://github.com/touwaeriol/sub2apipay) | 自助支付系统 | 用户自助充值、自助订阅购买；兼容易支付协议、微信官方支付、支付宝官方支付、Stripe |
 
 ## 技术栈