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

setting/user_usable_group.go

@@ -0,0 +1,54 @@
+package setting
+
+import (
+	"encoding/json"
+	"sync"
+
+	"github.com/QuantumNous/new-api/common"
+)
+
+var userUsableGroups = map[string]string{
+	"default": "默认分组",
+	"vip":     "vip分组",
+}
+var userUsableGroupsMutex sync.RWMutex
+
+func GetUserUsableGroupsCopy() map[string]string {
+	userUsableGroupsMutex.RLock()
+	defer userUsableGroupsMutex.RUnlock()
+
+	copyUserUsableGroups := make(map[string]string)
+	for k, v := range userUsableGroups {
+		copyUserUsableGroups[k] = v
+	}
+	return copyUserUsableGroups
+}
+
+func UserUsableGroups2JSONString() string {
+	userUsableGroupsMutex.RLock()
+	defer userUsableGroupsMutex.RUnlock()
+
+	jsonBytes, err := json.Marshal(userUsableGroups)
+	if err != nil {
+		common.SysLog("error marshalling user groups: " + err.Error())
+	}
+	return string(jsonBytes)
+}
+
+func UpdateUserUsableGroupsByJSONString(jsonStr string) error {
+	userUsableGroupsMutex.Lock()
+	defer userUsableGroupsMutex.Unlock()
+
+	userUsableGroups = make(map[string]string)
+	return json.Unmarshal([]byte(jsonStr), &userUsableGroups)
+}
+
+func GetUsableGroupDescription(groupName string) string {
+	userUsableGroupsMutex.RLock()
+	defer userUsableGroupsMutex.RUnlock()
+
+	if desc, ok := userUsableGroups[groupName]; ok {
+		return desc
+	}
+	return groupName
+}