feat: refine price formatting and enable dynamic color updates in cart

- Updated price slider and backend formatting to round values instead of showing decimals
- Enhanced product detail page with active color selection display and automatic cart updates
- Adjusted swatch behavior to dynamically update the selected color in the cart via AJAX
- Improved consistency in slider steps and price formatting throughout templates and views

static/js/catalog-price-slider.js

@@ -1,11 +1,11 @@
 document.addEventListener('DOMContentLoaded', function () {
     const priceFormatter = new Intl.NumberFormat('ru-RU', {
-        minimumFractionDigits: 2,
-        maximumFractionDigits: 2,
+        minimumFractionDigits: 0,
+        maximumFractionDigits: 0,
     });
 
     const formatQueryValue = function (value) {
-        return value.toFixed(2).replace(/\.?0+$/, '');
+        return Math.round(value).toString();
     };
 
     document.querySelectorAll('[data-price-slider]').forEach(function (slider) {