fix: surface frps startup failures and avoid nginx port conflicts

internal/frp/agent_client_test.go

@@ -0,0 +1,36 @@
+package frp
+
+import "testing"
+
+func TestNormalizeFRPSActionResult(t *testing.T) {
+	if _, err := normalizeFRPSActionResult(nil); err == nil {
+		t.Fatal("空响应应返回错误")
+	}
+	if _, err := normalizeFRPSActionResult(map[string]any{}); err == nil {
+		t.Fatal("缺少 ok 字段应返回错误")
+	}
+
+	failed, err := normalizeFRPSActionResult(map[string]any{
+		"ok":    false,
+		"error": "systemctl start 已执行但 frps 未进入运行状态",
+	})
+	if err != nil {
+		t.Fatalf("ok=false 应保留给前端展示，got %v", err)
+	}
+	if failed["ok"] != false || failed["error"] == "" {
+		t.Fatalf("失败结果未保留：%+v", failed)
+	}
+
+	failedWithoutMessage, err := normalizeFRPSActionResult(map[string]any{"ok": false})
+	if err != nil {
+		t.Fatalf("ok=false 应补齐默认错误，got %v", err)
+	}
+	if failedWithoutMessage["error"] != "frps 未进入运行状态，请查看 frps 日志" {
+		t.Fatalf("默认错误不正确：%+v", failedWithoutMessage)
+	}
+
+	success, err := normalizeFRPSActionResult(map[string]any{"ok": true, "action": "start"})
+	if err != nil || success["ok"] != true {
+		t.Fatalf("成功结果解析失败：result=%+v err=%v", success, err)
+	}
+}