refactor(service): 将 user.go 移动至 user_ser 子包

internal/service/user_ser/user.go

@@ -0,0 +1,14 @@
+package user_ser
+
+import (
+	"EnGin/internal/db"
+	"EnGin/internal/ent"
+	"context"
+)
+
+func CreateUser(ctx context.Context, username string) (*ent.User, error) {
+	// 💡 直接跨包调用 db.Client
+	return db.Client.User.Create().
+		// SetUsername(username).
+		Save(ctx)
+}