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

relay/channel/replicate/constants.go

@@ -0,0 +1,12 @@
+package replicate
+
+const (
+	// ChannelName identifies the replicate channel.
+	ChannelName = "replicate"
+	// ModelFlux11Pro is the default image generation model supported by this channel.
+	ModelFlux11Pro = "black-forest-labs/flux-1.1-pro"
+)
+
+var ModelList = []string{
+	ModelFlux11Pro,
+}