fix(backend): secure production startup and migrations

backend/internal/logic/search/service_postgres_test.go

@@ -4,15 +4,14 @@ package search
 
 import (
 	"fmt"
-	"os"
 	"strings"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/require"
-	"gorm.io/driver/postgres"
 	"gorm.io/gorm"
 	"senlinai-agent/backend/internal/models"
+	"senlinai-agent/backend/internal/testutil"
 )
 
 func TestPostgresSearchMatchesChinesePartialKeywords(t *testing.T) {
@@ -111,13 +110,7 @@ func TestPostgresSearchUsesStableFairLimitAndRuneBoundedSnippets(t *testing.T) {
 
 func newPostgresSearchTestDB(t *testing.T) *gorm.DB {
 	t.Helper()
-	dsn := os.Getenv("TEST_DATABASE_URL")
-	require.NotEmpty(t, dsn, "TEST_DATABASE_URL is required for integration tests and must point to an isolated database")
-	database, err := gorm.Open(postgres.Open(dsn), &gorm.Config{TranslateError: true})
-	require.NoError(t, err)
-	transaction := database.Begin()
-	require.NoError(t, transaction.Error)
-	t.Cleanup(func() { transaction.Rollback() })
-	require.NoError(t, models.AutoMigrate(transaction))
-	return transaction
+	database := testutil.OpenIsolatedPostgres(t, &gorm.Config{TranslateError: true})
+	require.NoError(t, models.AutoMigrate(database))
+	return database
 }