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/sub2api/adaptor.go

@@ -0,0 +1,17 @@
+package sub2api
+
+import (
+	"github.com/QuantumNous/new-api/relay/channel/newapi"
+)
+
+type Adaptor struct {
+	newapi.Adaptor
+}
+
+func (a *Adaptor) GetModelList() []string {
+	return ModelList
+}
+
+func (a *Adaptor) GetChannelName() string {
+	return ChannelName
+}

relay/channel/sub2api/adaptor_test.go

@@ -0,0 +1,46 @@
+package sub2api
+
+import (
+	"testing"
+
+	"github.com/QuantumNous/new-api/constant"
+	relaycommon "github.com/QuantumNous/new-api/relay/common"
+	relayconstant "github.com/QuantumNous/new-api/relay/constant"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetRequestURLAlphaSearch(t *testing.T) {
+	adaptor := &Adaptor{}
+	info := &relaycommon.RelayInfo{
+		ChannelMeta: &relaycommon.ChannelMeta{
+			ChannelType:    constant.ChannelTypeSub2API,
+			ChannelBaseUrl: "https://sub2api.example",
+		},
+		RequestURLPath: "/v1/alpha/search",
+		RelayMode:      relayconstant.RelayModeAlphaSearch,
+	}
+
+	url, err := adaptor.GetRequestURL(info)
+	require.NoError(t, err)
+	assert.Equal(t, "https://sub2api.example/v1/alpha/search", url)
+}
+
+func TestAdaptorInheritsNewAPIResponsesCompactSupport(t *testing.T) {
+	adaptor := &Adaptor{}
+	info := &relaycommon.RelayInfo{
+		ChannelMeta: &relaycommon.ChannelMeta{
+			ChannelType:    constant.ChannelTypeSub2API,
+			ChannelBaseUrl: "https://sub2api.example",
+		},
+		RequestURLPath: "/v1/responses/compact",
+		RelayMode:      relayconstant.RelayModeResponsesCompact,
+	}
+
+	url, err := adaptor.GetRequestURL(info)
+
+	require.NoError(t, err)
+	assert.Equal(t, "https://sub2api.example/v1/responses/compact", url)
+	assert.Equal(t, "sub2api", adaptor.GetChannelName())
+	assert.Empty(t, adaptor.GetModelList())
+}

relay/channel/sub2api/constants.go

@@ -0,0 +1,6 @@
+package sub2api
+
+const ChannelName = "sub2api"
+
+// ModelList is empty because models are fetched dynamically from upstream /v1/models.
+var ModelList = []string{}