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/request-id.go

@@ -0,0 +1,19 @@
+package middleware
+
+import (
+	"context"
+
+	"github.com/QuantumNous/new-api/common"
+	"github.com/gin-gonic/gin"
+)
+
+func RequestId() func(c *gin.Context) {
+	return func(c *gin.Context) {
+		id := common.NewRequestId()
+		c.Set(common.RequestIdKey, id)
+		ctx := context.WithValue(c.Request.Context(), common.RequestIdKey, id)
+		c.Request = c.Request.WithContext(ctx)
+		c.Header(common.RequestIdKey, id)
+		c.Next()
+	}
+}