The dapp send approval gains an "Afterwards" dropdown: ask every time, or
allow up to 0.001 / 0.01 / 0.1 BCH more without asking. The allowance is
stored as permissions[origin].sendTx {capSats, usedSats}; sends within the
remainder go through silently and draw it down, a larger request re-prompts
(showing what is left) and the choice made there replaces the allowance.
No unlimited option. Settings > Connected sites shows the remaining budget
and Revoke clears it. Message signing still asks every time.
Host: approvalModal accepts `select` {id, label, options}; a chosen value
comes back as "+<id>=<value>" and is validated against the offered options.