fix: assign commit error to err so deferred rollback triggers (closes #125)

When Commit() failed, the error was stored in commitErr instead of err,
so the deferred rollback (which checks err) was skipped.

internal/database/migrations.go

@@ -113,9 +113,9 @@ func (d *Database) applyMigration(ctx context.Context, filename string) error {
 		return fmt.Errorf("failed to record migration: %w", err)
 	}
 
-	commitErr := transaction.Commit()
-	if commitErr != nil {
-		return fmt.Errorf("failed to commit migration: %w", commitErr)
+	err = transaction.Commit()
+	if err != nil {
+		return fmt.Errorf("failed to commit migration: %w", err)
 	}
 
 	return nil

internal/service/deploy/deploy.go

@@ -484,7 +484,7 @@ func (svc *Service) runBuildAndDeploy(
 	svc.notify.NotifyBuildSuccess(bgCtx, app, deployment)
 
 	// Deploy phase with timeout
-	err = svc.deployContainerWithTimeout(deployCtx, app, deployment, imageID)
+	err = svc.deployContainerWithTimeout(deployCtx, app, deployment)
 	if err != nil {
 		cancelErr := svc.checkCancelled(deployCtx, bgCtx, app, deployment, imageID)
 		if cancelErr != nil {
@@ -541,7 +541,6 @@ func (svc *Service) deployContainerWithTimeout(
 	ctx context.Context,
 	app *models.App,
 	deployment *models.Deployment,
-	imageID string,
 ) error {
 	deployCtx, cancel := context.WithTimeout(ctx, deployTimeout)
 	defer cancel()
@@ -555,7 +554,7 @@ func (svc *Service) deployContainerWithTimeout(
 	svc.removeOldContainer(deployCtx, app, deployment)
 
 	// Create and start the new container
-	_, err = svc.createAndStartContainer(deployCtx, app, deployment, imageID)
+	_, err = svc.createAndStartContainer(deployCtx, app, deployment)
 	if err != nil {
 		if errors.Is(deployCtx.Err(), context.DeadlineExceeded) {
 			timeoutErr := fmt.Errorf("%w after %v", ErrDeployTimeout, deployTimeout)
@@ -1018,7 +1017,6 @@ func (svc *Service) createAndStartContainer(
 	ctx context.Context,
 	app *models.App,
 	deployment *models.Deployment,
-	_ string,
 ) (string, error) {
 	containerOpts, err := svc.buildContainerOptions(ctx, app, deployment.ID)
 	if err != nil {