Add .gitignore and project files

update_cart.php

@@ -0,0 +1,31 @@
+<?php
+session_start();
+require_once 'config/database.php';
+
+if (!isset($_SESSION['isLoggedIn']) || $_SESSION['isLoggedIn'] !== true) {
+    echo json_encode(['success' => false, 'message' => 'Требуется авторизация']);
+    exit();
+}
+
+if ($_SERVER['REQUEST_METHOD'] == 'POST' && isset($_POST['product_id'])) {
+    $product_id = intval($_POST['product_id']);
+    $quantity = intval($_POST['quantity'] ?? 1);
+    $user_id = $_SESSION['user_id'] ?? 0;
+
+    $db = Database::getInstance()->getConnection();
+
+    try {
+        $stmt = $db->prepare("
+            UPDATE cart
+            SET quantity = ?, updated_at = CURRENT_TIMESTAMP
+            WHERE user_id = ? AND product_id = ?
+        ");
+        $stmt->execute([$quantity, $user_id, $product_id]);
+
+        echo json_encode(['success' => true]);
+
+    } catch (PDOException $e) {
+        echo json_encode(['success' => false, 'message' => 'Ошибка базы данных']);
+    }
+}
+?>