Turn SendScene2 into a send-to-address swap (Stealth Send)

The send scene now offers a "Recipient receives" asset selector
(Houdini-served destination chains) and a Stealth Send toggle. Stealth
or a cross-asset recipient turns the send into a swap-to-address quote:
live quotes via account.fetchSwapQuotes with toAddressInfo, linked
"You send"/"Recipient gets" amount rows whose edited side is the
guaranteed amount, the shared price-impact indicator, a real expiry
countdown that re-quotes, the quote's network fee, and a destination
tag row on memoNeeded chains that rides toMemos to the provider.
Stealth restricts quotes to Houdini; a plain cross-asset send fans out
to every provider. The confirm slider approves the quote and lands on
the swap success scene.

Plain same-asset sends are unchanged, including multi-recipient UTXO
sends, which now also show a total-amount row. Multi-recipient and
stealth/cross-asset are mutually exclusive, gated in both directions.
Constrained callers (locked or hidden tiles, FIO requests, payment
protocol, custom broadcast/completion hooks) keep today's behavior.
Cross-chain destination addresses validate against the destination
chain's own rules via a new AddressTile2 validation override, since the
source wallet cannot parse them.

Author: j0ntz