feat: add favorites feature for users

- Implemented `Favorite` model with unique user-item constraint and timestamped records
- Added `favorites:index` and `favorites:toggle` views with AJAX support for toggling favorites
- Built templates and front-end assets for the favorites page and integration with item grids
- Extended header with favorites link and dynamic counter
- Added tests covering models, views, and templates for the favorites functionality
- Updated admin to enable management of favorites via Django admin interface

templates/favorites/index.html

@@ -0,0 +1,39 @@
+{% extends "_layouts/base.html" %}
+{% load static %}
+
+{% block title %}Избранное{% endblock %}
+
+{% block add_css %}
+    <link rel="stylesheet" href="{% static "css/catalog.css" %}">
+    <link rel="stylesheet" href="{% static "css/favorites.css" %}">
+{% endblock %}
+
+{% block content %}
+    {% include "_fragments/header.html" with active="favorites" %}
+
+    {% include '_fragments/breadcrumbs.html' with url_1='/' text_1='Главная' url_2='/favorites/' text_2='Избранное' %}
+
+    <main class="container favorites-page" data-favorites-page>
+        <section class="favorites-hero">
+            <p class="favorites-kicker">Личный список</p>
+            <div class="favorites-hero__row">
+                <div>
+                    <h1 class="favorites-title">Избранные товары</h1>
+                    <p class="favorites-description">
+                        Здесь собраны товары, которые вы хотите сохранить для быстрого возврата к ним позже.
+                    </p>
+                </div>
+                <div class="favorites-counter">
+                    <span class="favorites-counter__value" data-favorites-count-value>{{ favorite_count }}</span>
+                    <span class="favorites-counter__label" data-favorites-count-label>товаров</span>
+                </div>
+            </div>
+        </section>
+
+        <section class="favorites-list" aria-label="Список избранных товаров">
+            {% include "_fragments/item-grid.html" with items=items empty_message="В избранном пока нет товаров." favorites_grid=True %}
+        </section>
+    </main>
+
+    {% include "_fragments/footer.html" %}
+{% endblock %}