Exposes `resolve(sender_pubkey_hex) -> RouteHit | None` and a
`register_with_lnbits()` helper that lazily-imports + soft-fails on
lnbits versions without `register_roster_resolver`. Wired into
`satmachineadmin_start()`.
The hook delivers the path-B outcome ("cash-out sats go to the
operator's wallet, not an auto-created machine wallet") once the
lnbits side ships its half. Shape contract `(operator_user_id,
wallet_id, source_extension)` frozen per coord-log 2026-05-31T15:25Z.
Branch held local until lnbits lands the registry — no behaviour
change on the current lnbits version, just the future-ready handoff
+ a benign INFO log on boot.
Boot-smoked in dev container: extension loads, registration logs the
documented soft-fail message, invoice listener + cassette consumer
unchanged. 6 new unit tests cover happy path, miss, bech32 +
uppercase canonicalisation, fail-closed on malformed input, and the
soft-fail register branch.
