fix: 修复 TestSaveAndLoadConfig 测试隔离问题，使用临时目录替代真实用户配置

backend/tests/config/config_test.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v3"
 )
 
 func TestLoadConfig_DefaultValues(t *testing.T) {
@@ -135,21 +136,7 @@ func TestLoadConfig_AutoCreate(t *testing.T) {
 
 func TestSaveAndLoadConfig(t *testing.T) {
 	tmpDir := t.TempDir()
-
-	homeDir, err := os.UserHomeDir()
-	require.NoError(t, err)
-	nexDir := filepath.Join(homeDir, ".nex")
-	configPath := filepath.Join(nexDir, "config.yaml")
-
-	originalConfig, err := os.ReadFile(configPath)
-	if err != nil && !os.IsNotExist(err) {
-		require.NoError(t, err)
-	}
-	defer func() {
-		if originalConfig != nil {
-			require.NoError(t, os.WriteFile(configPath, originalConfig, 0o600))
-		}
-	}()
+	configPath := filepath.Join(tmpDir, "config.yaml")
 
 	cfg := &config.Config{
 		Server: config.ServerConfig{
@@ -176,10 +163,13 @@ func TestSaveAndLoadConfig(t *testing.T) {
 		},
 	}
 
-	err = config.SaveConfig(cfg)
+	data, err := yaml.Marshal(cfg)
 	require.NoError(t, err)
 
-	loaded, err := config.LoadConfig()
+	err = os.WriteFile(configPath, data, 0o600)
+	require.NoError(t, err)
+
+	loaded, err := config.LoadConfigFromPath(configPath)
 	require.NoError(t, err)
 
 	assert.Equal(t, cfg.Server.Port, loaded.Server.Port)