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

templates/catalog/detail.html

@@ -61,13 +61,14 @@
                 <div class="product-summary__swatches" aria-label="Цвета товара">
                     {% for color in colors %}
                         <span
-                            class="product-summary__swatch"
+                            class="product-summary__swatch{% if color.id == cart_color_id %} product-summary__swatch--active{% endif %}"
                             style="background: {{ color.hex_code }};"
                             title="{{ color.name }}"
                             data-color-id="{{ color.id }}"
                         ></span>
                     {% endfor %}
                 </div>
+                <p class="product-summary__color-name" data-color-name>{% for color in colors %}{% if color.id == cart_color_id %}Цвет: {{ color.name }}{% endif %}{% endfor %}</p>
             {% endif %}
             {% endwith %}
 
@@ -77,6 +78,12 @@
 
             <div class="product-summary__actions">
                 {% if item.id in cart_item_ids %}
+                    <form method="post" action="{% url 'orders:add' %}" class="product-summary__cart-form" id="update-color-form" style="display:none;">
+                        {% csrf_token %}
+                        <input type="hidden" name="item_id" value="{{ item.id }}">
+                        <input type="hidden" name="next" value="{{ request.get_full_path }}">
+                        <input type="hidden" name="color_id" id="selected-color-id" value="">
+                    </form>
                     <a class="product-summary__button product-summary__button--primary product-summary__button--link" href="{% url 'orders:cart' %}">
                         Перейти в корзину
                     </a>
@@ -115,18 +122,29 @@
         (function () {
             var swatches = document.querySelectorAll('.product-summary__swatch[data-color-id]');
             var colorInput = document.getElementById('selected-color-id');
+            var colorNameEl = document.querySelector('[data-color-name]');
+            var updateForm = document.getElementById('update-color-form');
             var cartBtn = document.querySelector('.product-summary__button--primary[type="submit"]');
 
             if (!swatches.length || !colorInput) { return; }
 
-            if (cartBtn) { cartBtn.disabled = true; }
+            if (!updateForm && cartBtn) { cartBtn.disabled = true; }
 
             swatches.forEach(function (swatch) {
                 swatch.addEventListener('click', function () {
                     swatches.forEach(function (s) { s.classList.remove('product-summary__swatch--active'); });
                     this.classList.add('product-summary__swatch--active');
                     colorInput.value = this.dataset.colorId || '';
-                    if (cartBtn) { cartBtn.disabled = false; }
+
+                    if (colorNameEl) {
+                        colorNameEl.textContent = 'Цвет: ' + this.title;
+                    }
+
+                    if (updateForm) {
+                        updateForm.submit();
+                    } else if (cartBtn) {
+                        cartBtn.disabled = false;
+                    }
                 });
             });
         }());