Fix account type not updating on edit

UpdateAccountRequest was missing the Type field, so changes to
account type were silently ignored. Add Type to the DTO and apply
it in the update service method.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/Purrse.Api/Services/AccountService.cs

@@ -60,6 +60,7 @@ public class AccountService : IAccountService
             ?? throw new KeyNotFoundException("Account not found");
 
         account.Name = request.Name;
+        account.Type = request.Type;
         account.Institution = request.Institution;
         account.AccountNumber = request.AccountNumber;
         account.CreditLimit = request.CreditLimit;