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.go

@@ -0,0 +1,65 @@
+package kitutil
+
+import (
+	"fmt"
+	"os"
+	"sync/atomic"
+)
+
+// Kit packages log rare data-shape anomalies through these hooks. The host
+// redirects them into its logging system at startup; standalone relaykit users
+// get stderr defaults.
+
+type LogFunc func(message string)
+
+var (
+	logInfo        atomic.Pointer[LogFunc]
+	logError       atomic.Pointer[LogFunc]
+	logSystemError atomic.Pointer[LogFunc]
+)
+
+func SetLogging(info LogFunc, errorFn LogFunc) {
+	if info != nil {
+		logInfo.Store(&info)
+	}
+	if errorFn != nil {
+		logError.Store(&errorFn)
+	}
+}
+
+// SetSystemErrorLogging configures the hook for internal converter failures.
+func SetSystemErrorLogging(errorFn LogFunc) {
+	if errorFn != nil {
+		logSystemError.Store(&errorFn)
+	}
+}
+
+func LogInfo(message string) {
+	if fn := logInfo.Load(); fn != nil {
+		(*fn)(message)
+		return
+	}
+	fmt.Fprintf(os.Stderr, "[relaykit] %s\n", message)
+}
+
+func LogError(message string) {
+	if fn := logError.Load(); fn != nil {
+		(*fn)(message)
+		return
+	}
+	fmt.Fprintf(os.Stderr, "[relaykit] ERROR %s\n", message)
+}
+
+// LogSystemError reports an internal converter failure through its dedicated
+// hook, keeping it distinct from malformed request-data diagnostics.
+func LogSystemError(message string) {
+	if fn := logSystemError.Load(); fn != nil {
+		(*fn)(message)
+		return
+	}
+	fmt.Fprintf(os.Stderr, "[relaykit] SYSTEM ERROR %s\n", message)
+}
+
+// Debug reports whether verbose kit diagnostics are enabled. The host sets
+// this once at startup (new-api mirrors common.DebugEnabled into it).
+var Debug atomic.Bool