refactor: 调整项目结构为单向依赖

backend/internal/service/api_key.go

@@ -0,0 +1,20 @@
+package service
+
+import "time"
+
+type ApiKey struct {
+	ID        int64
+	UserID    int64
+	Key       string
+	Name      string
+	GroupID   *int64
+	Status    string
+	CreatedAt time.Time
+	UpdatedAt time.Time
+	User      *User
+	Group     *Group
+}
+
+func (k *ApiKey) IsActive() bool {
+	return k.Status == StatusActive
+}