Replace manual SymmetricSecurityKey validation with Authority-based OIDC discovery so tokens are validated against RSA keys published by the IAM IdentityServer's discovery endpoint. Services updated: - CatalogService.API - OrderService.API - InventoryService.API - FnbEngine.API - BookingService.API Co-authored-by: Velik <hongochai10@users.noreply.github.com>