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

common/body_storage_test.go

@@ -0,0 +1,37 @@
+package common
+
+import (
+	"io"
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewReplayableBodyReaderKeepsStorageLifecycleWithCaller(t *testing.T) {
+	payload := []byte(`{"model":"test-model","input":"hello"}`)
+	storage, err := CreateBodyStorage(payload)
+	require.NoError(t, err)
+	defer storage.Close()
+
+	body := NewReplayableBodyReader(storage)
+	assert.EqualValues(t, len(payload), body.Size())
+	_, exposesCloser := any(body).(io.Closer)
+	assert.False(t, exposesCloser, "the request body must not expose the storage closer")
+
+	req, err := http.NewRequest(http.MethodPost, "https://example.com", body)
+	require.NoError(t, err)
+	require.NoError(t, req.Body.Close())
+
+	replayBody, err := body.NewReader()
+	require.NoError(t, err, "closing the HTTP request body must not close the storage")
+	replay, err := io.ReadAll(replayBody)
+	require.NoError(t, err)
+	require.NoError(t, replayBody.Close())
+	assert.Equal(t, payload, replay)
+
+	require.NoError(t, storage.Close())
+	_, err = body.NewReader()
+	require.ErrorIs(t, err, ErrStorageClosed)
+}