Feature request: Add "Privacy Mode"

This would be a setting defaulted to off.

With the setting on, we could blur out numbers and transaction totals with CSS (https://developer.mozilla.org/en-US/docs/Web/CSS/filter-function/blur());

This would enable people to keep account data (like balances and transaction amounts) private, even when others are seeing their screen.

No repository files, tests, or entry points are named. Start by locating the settings UI and account balances or transaction totals, then determine how the setting should control their CSS blur; done means an off-by-default Privacy Mode can blur those values when enabled.

Written by the indexing model from the issue text.