feat: Evotor + VK catalog sync, connections, and store/group filters

- Evotor catalog: background Celery task syncing stores/groups/products
  from Evotor API; UI pages with per-store and per-group sync toggles
- VK connection: manual token + group ID entry with inline test button
- Evotor connection: inline test button (calls /stores)
- VK catalog: background task syncing VK Market albums and products;
  separate catalog UI at /vk-catalog/albums
- SyncFilter extended to support entity_type=group with parent_entity_id
- Migration 0004: vk_cached_albums + vk_cached_products tables
- Beat schedule updated to run both refresh_catalog and refresh_vk_catalog
- README updated with new schema, routes, tasks, and config

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/templates/catalog/groups.html

@@ -0,0 +1,69 @@
+{% extends "base.html" %}
+{% block title %}Группы — {{ store.name }} — ЭВОСИНК{% endblock %}
+
+{% block content %}
+<nav aria-label="breadcrumb" class="mb-3">
+    <ol class="breadcrumb">
+        <li><a href="/catalog/stores">Магазины</a></li>
+        <li>{{ store.name }}</li>
+        <li>Группы</li>
+    </ol>
+</nav>
+
+<div class="d-flex justify-between align-center mb-3">
+    <h1 style="font-size:1.3rem; margin:0;"><i class="bi bi-folder me-2"></i>Группы товаров — {{ store.name }}</h1>
+    <span class="text-muted small">Всего: {{ groups | length }}</span>
+</div>
+
+<article class="card">
+    {% if groups %}
+    <div class="table-scroll">
+        <table class="align-middle">
+            <thead>
+                <tr>
+                    <th>Синхронизация</th>
+                    <th>Название</th>
+                    <th>ID</th>
+                    <th>Обновлено</th>
+                    <th></th>
+                </tr>
+            </thead>
+            <tbody>
+                {% for g in groups %}
+                {% set is_enabled = (enabled_ids is none) or (g.evotor_id in enabled_ids) %}
+                <tr class="{% if not is_enabled %}text-muted{% endif %}">
+                    <td>
+                        <form method="post" action="/catalog/stores/{{ store.evotor_id }}/groups/{{ g.evotor_id }}/toggle" style="margin:0;">
+                            <button type="submit"
+                                class="outline sm {% if is_enabled %}success{% else %}secondary{% endif %}"
+                                title="{% if is_enabled %}Отключить синхронизацию{% else %}Включить синхронизацию{% endif %}"
+                                style="padding:0.2rem 0.6rem;">
+                                {% if is_enabled %}
+                                    <i class="bi bi-toggle-on"></i>
+                                {% else %}
+                                    <i class="bi bi-toggle-off"></i>
+                                {% endif %}
+                            </button>
+                        </form>
+                    </td>
+                    <td><i class="bi bi-folder2 me-1 text-muted"></i> <strong>{{ g.name }}</strong></td>
+                    <td class="text-muted small">{{ g.evotor_id }}</td>
+                    <td class="text-muted small">{{ g.fetched_at | datefmt }}</td>
+                    <td>
+                        <a href="/catalog/stores/{{ store.evotor_id }}/products?group={{ g.evotor_id }}" role="button" class="outline sm">
+                            <i class="bi bi-box-seam"></i> Товары
+                        </a>
+                    </td>
+                </tr>
+                {% endfor %}
+            </tbody>
+        </table>
+    </div>
+    {% else %}
+    <div class="text-center py-5 text-muted">
+        <i class="bi bi-folder" style="font-size:2rem;"></i>
+        <p class="mt-2">Группы для этого магазина ещё не загружены.</p>
+    </div>
+    {% endif %}
+</article>
+{% endblock %}