Add NostrmarketAPI integration and enhance MerchantStore component

- Introduce NostrmarketAPI service for improved merchant profile management.
- Update MerchantStore component to handle loading and error states during merchant profile checks.
- Implement logic to check for merchant profiles using the new API, enhancing user experience.
- Refactor computed properties and lifecycle methods to accommodate the new API integration.

These changes streamline the process of checking and managing merchant profiles, providing users with real-time feedback and improving overall functionality.

src/core/di-container.ts

@@ -140,6 +140,7 @@ export const SERVICE_TOKENS = {
   
   // Nostrmarket services
   NOSTRMARKET_SERVICE: Symbol('nostrmarketService'),
+  NOSTRMARKET_API: Symbol('nostrmarketAPI'),
   
   // API services
   LNBITS_API: Symbol('lnbitsAPI'),