Remove useNostrOrders composable and related Checkout page

- Delete the useNostrOrders composable as it is no longer needed.
- Update MerchantStore.vue to utilize nostrmarketService for publishing orders instead of the removed composable.
- Refactor market store to check the readiness of nostrmarketService instead of useNostrOrders.
- Remove the Checkout.vue page, streamlining the checkout process and improving code maintainability.

src/modules/market/stores/market.ts

@@ -1,6 +1,5 @@
 import { defineStore } from 'pinia'
 import { ref, computed, readonly, watch } from 'vue'
-import { nostrOrders } from '@/composables/useNostrOrders'
 import { invoiceService } from '@/lib/services/invoiceService'
 import { paymentMonitor } from '@/lib/services/paymentMonitor'
 import { nostrmarketService } from '../services/nostrmarketService'
@@ -595,7 +594,7 @@ export const useMarketStore = defineStore('market', () => {
 
   const sendPaymentConfirmation = async (order: Order) => {
     try {
-      if (!nostrOrders.isReady.value) {
+      if (!nostrmarketService.isReady) {
         console.warn('Nostr not ready for payment confirmation')
         return
       }
@@ -612,7 +611,7 @@ export const useMarketStore = defineStore('market', () => {
       // }
 
       // Send confirmation to customer
-      await nostrOrders.publishOrderEvent(order, order.buyerPubkey)
+      await nostrmarketService.publishOrder(order, order.buyerPubkey)
       
       console.log('Payment confirmation sent via Nostr')
     } catch (error) {