Refactor wallet balance handling and integrate PaymentService for centralized management

- Replaced direct wallet balance computation in Navbar and WalletPage with a centralized totalBalance property from PaymentService, improving code maintainability.
- Updated CreateProductDialog, CreateStoreDialog, and MerchantStore components to utilize PaymentService for retrieving wallet admin and invoice keys, enhancing consistency across the application.
- These changes streamline wallet management and improve the overall architecture of the wallet module.

src/modules/market/components/MerchantStore.vue

@@ -353,6 +353,7 @@ import StoreCard from './StoreCard.vue'
 const router = useRouter()
 const marketStore = useMarketStore()
 const nostrmarketAPI = injectService(SERVICE_TOKENS.NOSTRMARKET_API) as NostrmarketAPI
+const paymentService = injectService(SERVICE_TOKENS.PAYMENT_SERVICE) as any
 const toast = useToast()
 
 // Local state
@@ -473,8 +474,15 @@ const loadStallsList = async () => {
   }
   
   isLoadingStalls.value = true
+
+  const inkey = paymentService.getPreferredWalletInvoiceKey()
+  if (!inkey) {
+    console.error('No wallet invoice key available')
+    return
+  }
+
   try {
-    const stalls = await nostrmarketAPI.getStalls(currentUser.wallets[0].inkey)
+    const stalls = await nostrmarketAPI.getStalls(inkey)
     userStalls.value = stalls || []
     
     // If there are stalls but no active one selected, select the first
@@ -496,9 +504,16 @@ const loadStallProducts = async () => {
   if (!currentUser?.wallets?.length) return
   
   isLoadingProducts.value = true
+
+  const inkey = paymentService.getPreferredWalletInvoiceKey()
+  if (!inkey) {
+    console.error('No wallet invoice key available')
+    return
+  }
+
   try {
     const products = await nostrmarketAPI.getProducts(
-      currentUser.wallets[0].inkey, 
+      inkey,
       activeStall.value.id!
     )
     stallProducts.value = products || []