Proposal for additional safety checks for recipient address

In order to minimize the possibility of sending funds to a wrong address, I propose to implement some simple additional checks of the destination address:
1. Log a history of sent-to account addresses and warn the user when sending to an address that was never used before.
2. Check the balance of the destination address and if 0 warn the user (reasoning: it might be either a never before used address or simply a wrong address).
3. Implement #2608

Start by reading the referenced issue #2608 and then locate the extension's transaction-sending flow. The issue names no files or tests, so confirm the intended scope and UX for address history and zero-balance warnings before implementation. Done means the agreed safety checks are implemented and verified without blocking valid transfers.

Written by the indexing model from the issue text.