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

model/db_time.go

@@ -0,0 +1,22 @@
+package model
+
+import "github.com/QuantumNous/new-api/common"
+
+// GetDBTimestamp returns a UNIX timestamp from database time.
+// Falls back to application time on error.
+func GetDBTimestamp() int64 {
+	var ts int64
+	var err error
+	switch {
+	case common.UsingMainDatabase(common.DatabaseTypePostgreSQL):
+		err = DB.Raw("SELECT EXTRACT(EPOCH FROM NOW())::bigint").Scan(&ts).Error
+	case common.UsingMainDatabase(common.DatabaseTypeSQLite):
+		err = DB.Raw("SELECT strftime('%s','now')").Scan(&ts).Error
+	default:
+		err = DB.Raw("SELECT UNIX_TIMESTAMP()").Scan(&ts).Error
+	}
+	if err != nil || ts <= 0 {
+		return common.GetTimestamp()
+	}
+	return ts
+}