test: add repository and domain tests

- Add pagination result tests (internal/repository/pagination.go)
- Add Gemini drive client factory test (internal/repository/gemini_drive_client.go)
- Add scanSingleRow contract tests (internal/repository/sql_scan.go)
- Add DefaultThemeConfig test (internal/domain/theme.go)

Coverage improvements:
- repository: 75.8%
- domain: 21.1%

internal/domain/table_name_test.go

@@ -98,6 +98,19 @@ func TestThemeConfig_TableName(t *testing.T) {
 	assert.Equal(t, "theme_configs", th.TableName())
 }
 
+// TestDefaultThemeConfig 测试默认主题配置
+func TestDefaultThemeConfig(t *testing.T) {
+	config := DefaultThemeConfig()
+	assert.NotNil(t, config)
+	assert.Equal(t, "default", config.Name)
+	assert.True(t, config.IsDefault)
+	assert.Equal(t, "#1890ff", config.PrimaryColor)
+	assert.Equal(t, "#52c41a", config.SecondaryColor)
+	assert.Equal(t, "#ffffff", config.BackgroundColor)
+	assert.Equal(t, "#333333", config.TextColor)
+	assert.True(t, config.Enabled)
+}
+
 // TestUserRole_TableName 测试用户角色表名
 func TestUserRole_TableName(t *testing.T) {
 	ur := UserRole{}