Add stock management, order notifications, webhooks, expiration cron, and billet type validation

- Decrement billet quantity after purchase in BilletOrderService::generateOrderTickets
- Block purchase when stock is exhausted (quantity <= 0) in OrderController::buildOrderItems
- Add organizer email notification on new order (order_notification_orga template)
- Add organizer email notification on cancel/refund (order_cancelled_orga template)
- Add ExpirePendingOrdersCommand (app:orders:expire-pending) cron every 5min via Ansible
  - Cancels pending orders older than 30 minutes, restores stock, invalidates tickets
  - Includes BilletBuyerRepository::findExpiredPending query method
  - 3 unit tests covering: no expired orders, stock restoration, unlimited billets
- Add payment_intent.payment_failed webhook: cancels order, logs audit, emails buyer
- Add charge.refunded webhook: sets order to refunded, invalidates tickets, notifies orga and buyer
- Validate billet type (billet/reservation_brocante/vote) against organizer offer
  - getAllowedBilletTypes: gratuit=billet only, basic/sur-mesure=all types
  - Server-side validation in hydrateBilletFromRequest, UI filtering in templates
- Update TASK_CHECKUP.md: all Billetterie & Commandes items now complete

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -13,6 +13,8 @@
     },
     "devDependencies": {
         "@happy-dom/global-registrator": "^20.8.4",
+        "@hotwired/stimulus": "^3.0.0",
+        "@spomky-labs/pwa-bundle": "file:vendor/spomky-labs/pwa-bundle/assets",
         "@tailwindcss/postcss": "^4.1.18",
         "@vitest/coverage-v8": "^4.1.0",
         "eslint": "9",