feat(api): implement centralized API client and refactor vendor pages

Introduced a new API client in src/lib/api/ to handle requests securely. Refactored vendor pages to use this client. Updated authentication logic in layout and login pages.

src/lib/api/index.ts

@@ -0,0 +1,3 @@
+// API Client exports
+export { api, authApi, companyApi, listingApi, listingsApi, stateApi, categoriesApi } from './client';
+export * from './types';