feat: 支持Anthropic API协议 | support Anthropic API protocol

- 添加Anthropic适配器实现 | Add Anthropic adaptor implementation
- 支持Anthropic消息格式转换 | Support Anthropic message format conversion
- 添加Vertex AI Claude适配器支持 | Add Vertex AI Claude adapter support
- 更新Anthropic的中继模式定义 | Update relay mode definitions for Anthropic
- 添加Anthropic控制器和路由 | Add Anthropic controller and routing

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: zgdmemail@gmail.com

router/relay.go

@@ -71,4 +71,16 @@ func SetRelayRouter(router *gin.Engine) {
 		relayV1Router.GET("/threads/:id/runs/:runsId/steps/:stepId", controller.RelayNotImplemented)
 		relayV1Router.GET("/threads/:id/runs/:runsId/steps", controller.RelayNotImplemented)
 	}
+
+	// Anthropic API compatibility - https://docs.anthropic.com/claude/reference/
+	anthropicRouter := router.Group("/anthropic")
+	anthropicRouter.Use(middleware.RelayPanicRecover(), middleware.TokenAuth(), middleware.Distribute())
+	{
+		// Models API
+		anthropicRouter.GET("/v1/models", controller.ListModels)
+		anthropicRouter.GET("/v1/models/:model", controller.RetrieveModel)
+
+		// Messages API - main endpoint for chat completions
+		anthropicRouter.POST("/v1/messages", controller.Relay)
+	}
 }