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

items/tests.py

@@ -2,6 +2,7 @@ from django.test import TestCase, override_settings
 from django.contrib.auth import get_user_model
 from django.core.exceptions import ValidationError
 
+from favorites.models import Favorite
 from items.models import Category, Item, ItemImage, Subcategory
 
 
@@ -52,7 +53,7 @@ class CatalogViewTests(TestCase):
         self.assertEqual(response.status_code, 200)
         self.assertContains(response, "Мойки")
         self.assertContains(response, "Смесители")
-        self.assertNotContains(response, "Подсветка")
+        self.assertNotContains(response, 'href="/catalog/decor/?subcategory=lights"')
 
     def test_subcategory_page_shows_only_selected_subcategory_items(self):
         Item.objects.create(
@@ -141,6 +142,36 @@ class CatalogViewTests(TestCase):
 
         self.assertContains(response, 'href="/catalog/plumbing/kitchen-sink/"')
 
+    def test_catalog_item_card_shows_favorite_button_for_authenticated_user(self):
+        user = get_user_model().objects.create_user(
+            username="ann",
+            email="ann@example.com",
+            password="StrongPassword123",
+            is_active=True,
+        )
+        self.client.force_login(user)
+
+        response = self.client.get("/catalog/")
+
+        self.assertContains(response, 'action="/favorites/toggle/"', html=False)
+        self.assertContains(response, "Добавить в избранное")
+        self.assertContains(response, 'name="item_id" value="', html=False)
+
+    def test_catalog_item_card_marks_favorited_item(self):
+        user = get_user_model().objects.create_user(
+            username="ann2",
+            email="ann2@example.com",
+            password="StrongPassword123",
+            is_active=True,
+        )
+        self.client.force_login(user)
+        Favorite.objects.create(user=user, item=self.sink)
+
+        response = self.client.get("/catalog/")
+
+        self.assertContains(response, "Удалить из избранного")
+        self.assertContains(response, "is-active")
+
     def test_detail_page_shows_item_data(self):
         ItemImage.objects.create(
             item=self.sink,

items/views.py

@@ -3,6 +3,7 @@ from dataclasses import dataclass
 from django.http import HttpRequest, HttpResponse, Http404
 from django.shortcuts import render
 
+from favorites.services import get_user_favorite_item_ids
 from items.models import Category, Item, Subcategory
 
 
@@ -56,6 +57,7 @@ def index(request: HttpRequest, category: str | None = None) -> HttpResponse:
         'items': items,
         'selected_category': selected_category,
         'selected_subcategory': selected_subcategory,
+        'favorite_item_ids': get_user_favorite_item_ids(request.user),
     })
 
 
@@ -76,4 +78,5 @@ def detail(request: HttpRequest, category: str, slug: str) -> HttpResponse:
         'item': item,
         'images': images,
         'primary_image': images[0] if images else None,
+        'favorite_item_ids': get_user_favorite_item_ids(request.user),
     })