feat: modernize wizard UX with smart rows, steppers, transitions, and edit links

- Hide montage toggles and dim furniture rows when quantity is 0
- Animate running totals bar with CSS transform instead of display toggle
- Add directional slide transitions (forward/backward) between steps
- Add +/- stepper buttons around quantity inputs for better affordance
- Increase mobile tap targets to 44px and show active step label
- Add "Edit" links to summary section headings for quick navigation
- Add "Step X of Y" counter below progress bar
- Add summaryEdit, stepLabel, stepOf l10n strings to both entry points

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

templates/form-page.php

@@ -40,6 +40,9 @@ $l10n_data = array(
 	'grandTotalLabel'    => __( 'Grand Total', 'siegel-umzugsliste' ),
 	'quantityLabel'      => __( 'Qty', 'siegel-umzugsliste' ),
 	'cbmLabel'           => __( 'cbm', 'siegel-umzugsliste' ),
+	'summaryEdit'        => __( 'Edit', 'siegel-umzugsliste' ),
+	'stepLabel'          => __( 'Step', 'siegel-umzugsliste' ),
+	'stepOf'             => __( 'of', 'siegel-umzugsliste' ),
 	'nonce'              => wp_create_nonce( 'umzugsliste_submit' ),
 );
 ?>