feat: 算力引擎 Go 后端核心（new-api）

- 统一 OpenAI 兼容 /v1 中继 + 渠道/额度/令牌/流水
- 各领域包：relay 模型网关、model 数据层、controller 管理 API

middleware/turnstile-check.go

@@ -0,0 +1,64 @@
+package middleware
+
+import (
+	"net/http"
+	"net/url"
+
+	"github.com/QuantumNous/new-api/common"
+	"github.com/gin-gonic/gin"
+)
+
+type turnstileCheckResponse struct {
+	Success bool `json:"success"`
+}
+
+func TurnstileCheck() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		if common.TurnstileCheckEnabled {
+			response := c.Query("turnstile")
+			if response == "" {
+				c.JSON(http.StatusOK, gin.H{
+					"success": false,
+					"message": "Turnstile token 为空",
+				})
+				c.Abort()
+				return
+			}
+			rawRes, err := http.PostForm("https://challenges.cloudflare.com/turnstile/v0/siteverify", url.Values{
+				"secret":   {common.TurnstileSecretKey},
+				"response": {response},
+				"remoteip": {c.ClientIP()},
+			})
+			if err != nil {
+				common.SysLog(err.Error())
+				c.JSON(http.StatusOK, gin.H{
+					"success": false,
+					"message": err.Error(),
+				})
+				c.Abort()
+				return
+			}
+			defer rawRes.Body.Close()
+			var res turnstileCheckResponse
+			err = common.DecodeJson(rawRes.Body, &res)
+			if err != nil {
+				common.SysLog(err.Error())
+				c.JSON(http.StatusOK, gin.H{
+					"success": false,
+					"message": err.Error(),
+				})
+				c.Abort()
+				return
+			}
+			if !res.Success {
+				c.JSON(http.StatusOK, gin.H{
+					"success": false,
+					"message": "Turnstile 校验失败，请刷新重试！",
+				})
+				c.Abort()
+				return
+			}
+		}
+		c.Next()
+	}
+}