refactor(autoload): migrate theme classes to Composer PSR-4

Move 288 types from global AKSRT_* + inc/classes manual requires into
namespace AKSRT\{Domain} under src/AKSRT/, wire composer.json psr-4,
and slim bootstrap to helpers/modules/hooks only. Split multi-class
widget/gateway files, update admin contract audit paths, and document
the layout in ADR/README.

src/AKSRT/Shop/CartService.php

@@ -0,0 +1,173 @@
+<?php
+/**
+ * @package AKSRT
+ */
+
+namespace AKSRT\Shop;
+
+defined('ABSPATH') || exit;
+
+class CartService {
+
+    private Shop $shop;
+
+    public function __construct(Shop $shop) {
+        $this->shop = $shop;
+    }
+
+    public function get_cart(int $user_id): array {
+        if ($user_id <= 0) {
+            return [];
+        }
+        $cart = get_user_meta($user_id, 'shop_cart', true);
+        return is_array($cart) ? $cart : [];
+    }
+
+    public function get_cart_count(int $user_id): int {
+        $cart = $this->get_cart($user_id);
+        $count = 0;
+        foreach ($cart as $opts) {
+            if (is_array($opts)) {
+                foreach ($opts as $qty) {
+                    $count += (int) $qty;
+                }
+            }
+        }
+        return $count;
+    }
+
+    public function add_to_cart(int $user_id, int $product_id, string $options_string = '', int $count = 1): array {
+        if ($user_id <= 0 || $product_id <= 0 || $count <= 0) {
+            return ['error' => 'invalid_params'];
+        }
+        $validation = $this->validate_cart_item($product_id, $options_string);
+        if ($validation !== true) {
+            return ['error' => $validation];
+        }
+
+        $cart = $this->get_cart($user_id);
+        $pid_key = (string) $product_id;
+        $opt_key = $options_string !== '' ? $options_string : '_default';
+
+        if (!isset($cart[$pid_key]) || !is_array($cart[$pid_key])) {
+            $cart[$pid_key] = [];
+        }
+        $cart[$pid_key][$opt_key] = ((int) ($cart[$pid_key][$opt_key] ?? 0)) + $count;
+
+        // Enforce limit_buy if set
+        $limit = (int) get_post_meta($product_id, '_aksrt_limit_buy', true);
+        if ($limit > 0 && $cart[$pid_key][$opt_key] > $limit) {
+            $cart[$pid_key][$opt_key] = $limit;
+        }
+
+        update_user_meta($user_id, 'shop_cart', $cart);
+        return ['success' => true, 'cart_count' => $this->get_cart_count($user_id)];
+    }
+
+    public function reduce_from_cart(int $user_id, int $product_id, string $options_string = '', int $count = 1): array {
+        if ($user_id <= 0 || $product_id <= 0 || $count <= 0) {
+            return ['error' => 'invalid_params'];
+        }
+        $cart = $this->get_cart($user_id);
+        $pid_key = (string) $product_id;
+        $opt_key = $options_string !== '' ? $options_string : '_default';
+
+        if (isset($cart[$pid_key][$opt_key])) {
+            $cart[$pid_key][$opt_key] -= $count;
+            if ($cart[$pid_key][$opt_key] <= 0) {
+                unset($cart[$pid_key][$opt_key]);
+            }
+        }
+        if (empty($cart[$pid_key])) {
+            unset($cart[$pid_key]);
+        }
+
+        update_user_meta($user_id, 'shop_cart', $cart);
+        return ['success' => true, 'cart_count' => $this->get_cart_count($user_id)];
+    }
+
+    public function remove_from_cart(int $user_id, int $product_id, string $options_string = ''): array {
+        if ($user_id <= 0) {
+            return ['error' => 'invalid_params'];
+        }
+        $cart = $this->get_cart($user_id);
+        $pid_key = (string) $product_id;
+        $opt_key = $options_string !== '' ? $options_string : '_default';
+
+        if ($options_string === '' && isset($cart[$pid_key])) {
+            // Remove all options for this product
+            unset($cart[$pid_key]);
+        } elseif (isset($cart[$pid_key][$opt_key])) {
+            unset($cart[$pid_key][$opt_key]);
+            if (empty($cart[$pid_key])) {
+                unset($cart[$pid_key]);
+            }
+        }
+
+        update_user_meta($user_id, 'shop_cart', $cart);
+        return ['success' => true, 'cart_count' => $this->get_cart_count($user_id)];
+    }
+
+    public function remove_multi_from_cart(int $user_id, array $items): array {
+        if ($user_id <= 0) {
+            return ['error' => 'invalid_params'];
+        }
+        $cart = $this->get_cart($user_id);
+        foreach ($items as $item) {
+            $pid_key = (string) ($item['product_id'] ?? 0);
+            $opt_key = !empty($item['options_string']) ? $item['options_string'] : '_default';
+            if (isset($cart[$pid_key][$opt_key])) {
+                unset($cart[$pid_key][$opt_key]);
+                if (empty($cart[$pid_key])) {
+                    unset($cart[$pid_key]);
+                }
+            }
+        }
+        update_user_meta($user_id, 'shop_cart', $cart);
+        return ['success' => true, 'cart_count' => $this->get_cart_count($user_id)];
+    }
+
+    public function empty_cart(int $user_id): array {
+        if ($user_id <= 0) {
+            return ['error' => 'invalid_params'];
+        }
+        delete_user_meta($user_id, 'shop_cart');
+        return ['success' => true, 'cart_count' => 0];
+    }
+
+    /**
+     * Validate a product for cart addition.
+     * Returns true if valid, or a string error code.
+     */
+    public function validate_cart_item(int $product_id, string $options_string = '') {
+        $post = get_post($product_id);
+        if (!$post || $post->post_type !== 'aksrt_product') {
+            return 'invalid_product';
+        }
+        if ($post->post_status !== 'publish') {
+            return 'product_not_published';
+        }
+
+        // Check stock (unless unlimited)
+        $stock = (int) get_post_meta($product_id, '_aksrt_stock', true);
+        if ($stock > -1 && $stock <= 0) {
+            return 'out_of_stock';
+        }
+
+        // Check guest_buy — if disabled and user not logged in
+        if (!is_user_logged_in()) {
+            $guest = get_post_meta($product_id, '_aksrt_guest_buy', true);
+            if ($guest === '0' || $guest === '') {
+                // Fall back to inheritance chain via TermMeta
+                if (class_exists('TermMeta')) {
+                    $resolved = TermMeta::resolve_inheritance($product_id, 'guest_buy');
+                    if (empty($resolved)) {
+                        return 'login_required';
+                    }
+                }
+            }
+        }
+
+        return true;
+    }
+}