fix: enforce stock limits on basket quantities

No stock validation existed in the ordering flow, allowing customers
to order more items than available.

Cap quantity to ``stock_current`` in ``Baskets::getBasketData()`` when
adding to cart. Add ``min=1`` and ``max=stock`` attributes on the
basket quantity input, with JS clamping in the change handler.
Verify stock again in ``Shop\OrderController::store()`` before saving
the order as a race-condition safeguard.

resources/views/Shop/Articles/partials/addBasket.blade.php

@@ -18,8 +18,9 @@
                 'name' => 'quantity',
                 'class' => 'quantity',
                 'id_name' => $model . '-quantity',
-                'value' => (int) $data[0]['prices'][0]['quantity'],
-                'min' => $data[0]['prices'][0]['quantity'],
+                'value' => 1,
+                'min' => 1,
+                'max' => $data[0]['stock'] ?? false,
                 'step' => 1,
             ])
         </div>
@@ -44,10 +45,35 @@
 
 @push('js')
     <script>
+        var {{ $model }}Stocks = {
+            @foreach ($data as $offer)
+                {{ $offer['id'] }}: {{ $offer['stock'] !== null ? $offer['stock'] : 'null' }},
+            @endforeach
+        };
+
+        function update{{ ucfirst($model) }}Max() {
+            var offerId = $('#{{ $model }}-offer_id').find('option:selected').val();
+            var stock = {{ $model }}Stocks[offerId];
+            var input = $('#{{ $model }}-quantity');
+            if (stock !== null && stock !== undefined) {
+                input.attr('max', stock);
+                if (parseInt(input.val()) > stock) {
+                    input.val(stock);
+                }
+            } else {
+                input.removeAttr('max');
+            }
+            if (parseInt(input.val()) < 1) {
+                input.val(1);
+            }
+        }
+
         $('#{{ $model }}-quantity').change(function() {
+            update{{ ucfirst($model) }}Max();
             setPrice('{{ $model }}');
         });
         $('#{{ $model }}-offer_id').change(function() {
+            update{{ ucfirst($model) }}Max();
             setPrice('{{ $model }}');
         });
     </script>