Fix N+1 query issues across order processing and menu display

[Copilot]

Database queries in order processing, menu display, and statistics views were triggering N+1 patterns, causing significant performance degradation under load.

Changes

pos_server/models.py

• Dish.serialize_with_options(): Prefetch components/child_dishes, compute only_choices inline to avoid redundant query

pos_server/views.py

• order_marking(), active_orders(): Add prefetch_related('orderdish_set__dish', 'delivery') and select_related('authorization')
• pos() POST: Batch fetch dishes instead of per-item queries
• day_stats(): Prefetch full order→dish→component→ingredient chain
• compile_menu(): Prefetch dishcomponent_set__component__child_dishes
• collect_order(): Use order.orderdish_set.all() to leverage prefetched data

online_store/views.py

• dish(): Prefetch allergen chain dishcomponent_set__component__componentingredient_set__ingredient
• place_order(): Batch fetch dishes with prefetched components

deliveries/views.py

• ready_orders(): Replace Python iteration with single filtered query
• profile(): Replace loop with .exists() check

inventory/views.py

• craft_component(): Prefetch componentingredient_set__ingredient

Example

Before:

for dish_id, quantity in dish_counts.items():
    dish = Dish.objects.get(id=dish_id)  # N queries

After:

dishes_queryset = Dish.objects.filter(id__in=dish_ids).prefetch_related(
    'components__child_dishes',
    'dishcomponent_set__component'
)
dishes_map = {dish.id: dish for dish in dishes_queryset}  # 1 query

Also added warning logs for missing dishes during order processing.

Original prompt

Identify and suggest improvements to slow or inefficient code

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