refactor backend packages and global db service

backend/internal/models/postgres_integration_test.go

@@ -0,0 +1,24 @@
+//go:build integration
+
+package models
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestPostgresPing(t *testing.T) {
+	dsn := os.Getenv("DATABASE_DSN")
+	if dsn == "" {
+		dsn = os.Getenv("DATABASE_URL")
+	}
+	require.NotEmpty(t, dsn, "DATABASE_DSN or DATABASE_URL is required for integration tests")
+
+	database, err := Open(dsn)
+	require.NoError(t, err)
+	sqlDB, err := database.DB()
+	require.NoError(t, err)
+	require.NoError(t, sqlDB.Ping())
+}