feat: implement order management and checkout functionality

- Added `Order` and `OrderItem` models with migrations for managing orders and their details
- Created `CheckoutForm` for validating order data and customer information
- Built templates for order confirmation, checkout success, and emails (HTML and plain text)
- Added logic for email notifications upon successful order placement
- Enhanced shopping cart template with checkout panel integration
- Updated styles and JavaScript for streamlined checkout UX
- Refactored cart view to support item summaries and final totals during checkout

static/js/cart.js

@@ -17,4 +17,46 @@ document.addEventListener('DOMContentLoaded', function () {
             }
         });
     });
+
+    const checkoutForm = document.querySelector('[data-checkout-form]');
+    if (!checkoutForm) {
+        return;
+    }
+
+    const productsTotal = Number(checkoutForm.dataset.productsTotal || '0');
+    const deliveryPrice = 500;
+    const floorLiftPrice = 45;
+    const totalNodes = document.querySelectorAll('[data-checkout-total-text]');
+    const deliveryNode = document.querySelector('[data-delivery-total-text]');
+    const floorLiftNode = document.querySelector('[data-floor-lift-total-text]');
+
+    const formatCurrency = function (value) {
+        return new Intl.NumberFormat('ru-RU', {
+            minimumFractionDigits: 2,
+            maximumFractionDigits: 2,
+        }).format(value) + ' руб.';
+    };
+
+    const updateCheckoutTotals = function () {
+        const selectedDelivery = checkoutForm.querySelector('input[name="delivery_method"]:checked');
+        const hasDelivery = selectedDelivery && selectedDelivery.value === 'courier';
+        const deliveryTotal = hasDelivery ? deliveryPrice : 0;
+        const floorLiftTotal = hasDelivery ? floorLiftPrice : 0;
+        const total = productsTotal + deliveryTotal + floorLiftTotal;
+
+        totalNodes.forEach(function (node) {
+            node.textContent = formatCurrency(total);
+        });
+        if (deliveryNode) {
+            deliveryNode.textContent = formatCurrency(deliveryTotal);
+        }
+        if (floorLiftNode) {
+            floorLiftNode.textContent = formatCurrency(floorLiftTotal);
+        }
+    };
+
+    checkoutForm.querySelectorAll('input[name="delivery_method"]').forEach(function (input) {
+        input.addEventListener('change', updateCheckoutTotals);
+    });
+    updateCheckoutTotals();
 });