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

controller/system_info.go

@@ -0,0 +1,65 @@
+package controller
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/QuantumNous/new-api/common"
+	"github.com/QuantumNous/new-api/model"
+
+	"github.com/gin-gonic/gin"
+)
+
+func ListSystemInstances(c *gin.Context) {
+	instances, err := model.ListSystemInstances()
+	if err != nil {
+		common.ApiError(c, err)
+		return
+	}
+
+	now := common.GetTimestamp()
+	responses := make([]model.SystemInstanceResponse, 0, len(instances))
+	for _, instance := range instances {
+		responses = append(responses, instance.ToResponse(now))
+	}
+
+	c.JSON(http.StatusOK, gin.H{
+		"success": true,
+		"message": "",
+		"data":    responses,
+	})
+}
+
+func DeleteStaleSystemInstances(c *gin.Context) {
+	deletedCount, err := model.DeleteStaleSystemInstances(common.GetTimestamp())
+	if err != nil {
+		common.ApiError(c, err)
+		return
+	}
+
+	common.ApiSuccess(c, gin.H{
+		"deleted_count": deletedCount,
+	})
+}
+
+func DeleteStaleSystemInstance(c *gin.Context) {
+	nodeName := c.Param("node_name")
+	if strings.TrimSpace(nodeName) == "" {
+		common.ApiErrorMsg(c, "node name is required")
+		return
+	}
+
+	deleted, err := model.DeleteStaleSystemInstance(nodeName, common.GetTimestamp())
+	if err != nil {
+		common.ApiError(c, err)
+		return
+	}
+	if !deleted {
+		common.ApiErrorMsg(c, "instance is not stale or no longer exists")
+		return
+	}
+
+	common.ApiSuccess(c, gin.H{
+		"deleted_count": 1,
+	})
+}