Enhance product handling in MerchantStore and useMarket

- Enriched products with stall names in MerchantStore, ensuring each product displays the associated stall name or 'Unknown Stall' if not available.
- Updated product addition logic in useMarket to include stall names, improving clarity and consistency across the application.
- Enhanced error handling for product loading to maintain robust functionality.

These changes improve the user experience by providing clearer product information in the market interface.

src/modules/market/components/MerchantStore.vue

@@ -516,7 +516,17 @@ const loadStallProducts = async () => {
       inkey,
       activeStall.value.id!
     )
-    stallProducts.value = products || []
+    // Enrich products with stall name
+    const enrichedProducts = (products || []).map(product => ({
+      ...product,
+      stallName: activeStall.value?.name || 'Unknown Stall'
+    }))
+    stallProducts.value = enrichedProducts
+
+    // Also add them to the market store so they appear in the main market
+    enrichedProducts.forEach(product => {
+      marketStore.addProduct(product)
+    })
   } catch (error) {
     console.error('Failed to load products:', error)
     stallProducts.value = []