Assign logo to accounts

Manual accounts usually still represent actual banks or specific apps. Without an assigned logo, it's often quite difficult to find the account you're looking for in a list of others. The app already has a good "Logo or Initials" implementation for Subscriptions and Payees – the same functionality can be reused for accounts, so that in the dropdowns, the sidebar, and a dedicated page it will be easier to distinguish the account you're looking for from the rest.

The same logic can be applied for the accounts groups.