Blockbook history is enabled by default (existing configs migrated once
via a v2 marker; a later deliberate opt-out sticks). The in-panel opt-in
prompt is replaced by a one-line note when it is off.
All displayed DGB amounts go through one formatter: thousands separators,
trailing zeros trimmed, never fewer than two decimals (3,811.32468574,
5.00, 0.0003345). Amount-field values keep full precision.
