Add full CRUD interface for Showcase management

Implemented complete web interface for managing showcases (display areas for ready-made bouquets) with:

**Backend:**
- ShowcaseForm with validation (unique name per warehouse)
- ShowcaseListView with filtering by warehouse and status
- ShowcaseCreateView, ShowcaseUpdateView with success messages
- ShowcaseDeleteView with active reservation validation
- URL routes: list, create, edit, delete

**Frontend:**
- List page with warehouse grouping, active reservations count
- Responsive table with filters (warehouse, status)
- Create/edit form with Bootstrap styling
- Delete confirmation with active reservations check
- Breadcrumb navigation

**Features:**
✅ One warehouse can have multiple showcases (ForeignKey relationship)
✅ Unique showcase names within each warehouse
✅ Display active reservation counts for each showcase
✅ Prevent deletion if showcase has active reservations
✅ Auto-select default warehouse when creating showcase
✅ Navigation link added to main navbar between "Касса" and "Склад"
✅ Active state highlighting in navigation

**Files created:**
- inventory/forms_showcase.py (ShowcaseForm)
- inventory/views/showcase.py (4 CBV views)
- inventory/templates/inventory/showcase/ (list, form, delete templates)

**Files modified:**
- inventory/urls.py (added showcase routes)
- inventory/forms.py (added Showcase import)
- templates/navbar.html (added "Витрины" link)

URL structure:
/inventory/showcases/ - list
/inventory/showcases/create/ - create
/inventory/showcases/<id>/edit/ - edit
/inventory/showcases/<id>/delete/ - delete

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

myproject/inventory/views/showcase.py

@@ -0,0 +1,175 @@
+# -*- coding: utf-8 -*-
+from django.contrib.auth.decorators import login_required
+from django.contrib import messages
+from django.shortcuts import render, redirect, get_object_or_404
+from django.db.models import Count, Q
+from django.views.generic import ListView, CreateView, UpdateView, DeleteView
+from django.urls import reverse_lazy
+from django.utils.decorators import method_decorator
+
+from inventory.models import Showcase, Reservation
+from inventory.forms_showcase import ShowcaseForm
+
+
+@method_decorator(login_required, name='dispatch')
+class ShowcaseListView(ListView):
+    """
+    Список всех витрин с группировкой по складам.
+    Отображает информацию о количестве активных резервов на каждой витрине.
+    """
+    model = Showcase
+    template_name = 'inventory/showcase/list.html'
+    context_object_name = 'showcases'
+
+    def get_queryset(self):
+        """
+        Получаем витрины с аннотацией количества активных резервов.
+        Сортируем по складу и названию.
+        """
+        queryset = Showcase.objects.select_related('warehouse').annotate(
+            active_reservations_count=Count(
+                'reservations',
+                filter=Q(reservations__status='reserved')
+            )
+        ).order_by('warehouse__name', 'name')
+
+        # Фильтрация по складу, если указан GET-параметр
+        warehouse_id = self.request.GET.get('warehouse')
+        if warehouse_id:
+            queryset = queryset.filter(warehouse_id=warehouse_id)
+
+        # Фильтрация по статусу активности
+        is_active = self.request.GET.get('is_active')
+        if is_active == '1':
+            queryset = queryset.filter(is_active=True)
+        elif is_active == '0':
+            queryset = queryset.filter(is_active=False)
+
+        return queryset
+
+    def get_context_data(self, **kwargs):
+        context = super().get_context_data(**kwargs)
+        context['title'] = 'Витрины'
+
+        # Добавляем информацию для фильтров
+        from inventory.models import Warehouse
+        context['warehouses'] = Warehouse.objects.filter(is_active=True).order_by('name')
+
+        return context
+
+
+@method_decorator(login_required, name='dispatch')
+class ShowcaseCreateView(CreateView):
+    """
+    Создание новой витрины.
+    """
+    model = Showcase
+    form_class = ShowcaseForm
+    template_name = 'inventory/showcase/form.html'
+    success_url = reverse_lazy('inventory:showcase-list')
+
+    def form_valid(self, form):
+        """Сохраняем витрину и показываем сообщение об успехе"""
+        response = super().form_valid(form)
+        messages.success(
+            self.request,
+            f'Витрина "{self.object.name}" успешно создана на складе "{self.object.warehouse.name}"'
+        )
+        return response
+
+    def get_context_data(self, **kwargs):
+        context = super().get_context_data(**kwargs)
+        context['title'] = 'Создание витрины'
+        context['form_title'] = 'Новая витрина'
+        context['submit_text'] = 'Создать витрину'
+        return context
+
+
+@method_decorator(login_required, name='dispatch')
+class ShowcaseUpdateView(UpdateView):
+    """
+    Редактирование существующей витрины.
+    """
+    model = Showcase
+    form_class = ShowcaseForm
+    template_name = 'inventory/showcase/form.html'
+    success_url = reverse_lazy('inventory:showcase-list')
+
+    def form_valid(self, form):
+        """Сохраняем изменения и показываем сообщение об успехе"""
+        response = super().form_valid(form)
+        messages.success(
+            self.request,
+            f'Витрина "{self.object.name}" успешно обновлена'
+        )
+        return response
+
+    def get_context_data(self, **kwargs):
+        context = super().get_context_data(**kwargs)
+        context['title'] = f'Редактирование витрины: {self.object.name}'
+        context['form_title'] = f'Редактирование: {self.object.name}'
+        context['submit_text'] = 'Сохранить изменения'
+
+        # Добавляем информацию о резервах на витрине
+        context['active_reservations_count'] = Reservation.objects.filter(
+            showcase=self.object,
+            status='reserved'
+        ).count()
+
+        return context
+
+
+@method_decorator(login_required, name='dispatch')
+class ShowcaseDeleteView(DeleteView):
+    """
+    Удаление витрины с подтверждением.
+    Проверяет наличие активных резервов перед удалением.
+    """
+    model = Showcase
+    template_name = 'inventory/showcase/delete.html'
+    success_url = reverse_lazy('inventory:showcase-list')
+
+    def get_context_data(self, **kwargs):
+        context = super().get_context_data(**kwargs)
+        context['title'] = f'Удаление витрины: {self.object.name}'
+
+        # Проверяем наличие активных резервов
+        active_reservations = Reservation.objects.filter(
+            showcase=self.object,
+            status='reserved'
+        ).select_related('product')
+
+        context['active_reservations'] = active_reservations
+        context['has_active_reservations'] = active_reservations.exists()
+
+        return context
+
+    def delete(self, request, *args, **kwargs):
+        """Проверяем наличие активных резервов перед удалением"""
+        showcase = self.get_object()
+
+        # Проверка активных резервов
+        active_reservations_count = Reservation.objects.filter(
+            showcase=showcase,
+            status='reserved'
+        ).count()
+
+        if active_reservations_count > 0:
+            messages.error(
+                request,
+                f'Невозможно удалить витрину "{showcase.name}": '
+                f'на ней есть {active_reservations_count} активных резервов. '
+                'Сначала освободите или продайте зарезервированные товары.'
+            )
+            return redirect('inventory:showcase-delete', pk=showcase.pk)
+
+        # Удаляем витрину
+        showcase_name = showcase.name
+        response = super().delete(request, *args, **kwargs)
+
+        messages.success(
+            request,
+            f'Витрина "{showcase_name}" успешно удалена'
+        )
+
+        return response