fix(quantity): enforce claim limits on backend, fix quantity field in admin form

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

components/admin/ItemForm.tsx

@@ -65,6 +65,21 @@ export default function ItemForm({ item, onSubmit, onCancel, mode, error }: Item
             }
           />
         </div>
+        <div>
+          <label className="block text-base font-medium text-gray-700 dark:text-gray-300 mb-1">
+            Quantidade
+          </label>
+          <input
+            type="number"
+            min={1}
+            required
+            className="w-full px-2 py-1.5 text-base border border-gray-300 dark:border-gray-600 rounded focus:outline-none focus:ring-2 focus:ring-indigo-500 dark:bg-gray-700 dark:text-white"
+            value={formData.quantity ?? 1}
+            onChange={(e) =>
+              setFormData((prev) => ({ ...prev, quantity: Math.max(1, parseInt(e.target.value) || 1) }))
+            }
+          />
+        </div>
         <div className="md:col-span-2">
           <label className="block text-base font-medium text-gray-700 dark:text-gray-300 mb-1">
             Description