Show/hide toggle for bank account and routing numbers when entering vendor payout details

Description:
When entering a vendor's bank details under Payout destination, the account and routing numbers are masked with asterisks as you type. This keeps sensitive info protected, but it makes it hard to double check the numbers while entering them, which increases the risk of a typo sending a payment to the wrong account or causing it to fail.

Suggested solution:
Add an eye icon next to the account and routing number fields so users can temporarily reveal what they've typed, then hide it again. The numbers would stay masked by default, and existing saved numbers would still never load back into the form.

Why it matters:

• Makes it easier to verify bank details against the vendor's form before saving

• Reduces the chance of failed or misdirected ACH payments caused by a mistyped digit

• Keeps the current security protections in place, since numbers stay hidden unless the user chooses to reveal them

Requested by: Genova Construction (Featurebase conversation 1304)