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

relaykit/relayconvert/kitutil/log_test.go

@@ -0,0 +1,31 @@
+package kitutil
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestErrorHooksRemainDistinct(t *testing.T) {
+	previousError := logError.Load()
+	previousSystemError := logSystemError.Load()
+	t.Cleanup(func() {
+		logError.Store(previousError)
+		logSystemError.Store(previousSystemError)
+	})
+
+	var ordinaryMessages []string
+	var systemMessages []string
+	SetLogging(nil, func(message string) {
+		ordinaryMessages = append(ordinaryMessages, message)
+	})
+	SetSystemErrorLogging(func(message string) {
+		systemMessages = append(systemMessages, message)
+	})
+
+	LogError("invalid dto")
+	LogSystemError("converter failure")
+
+	assert.Equal(t, []string{"invalid dto"}, ordinaryMessages)
+	assert.Equal(t, []string{"converter failure"}, systemMessages)
+}