feat(v2): nostr-transport roster-resolver hook (#20 path-B)

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.

__init__.py

@@ -5,6 +5,7 @@ from lnbits.tasks import create_permanent_unique_task
 from loguru import logger
 
 from .crud import db
+from .nostr_transport_roster import register_with_lnbits as register_roster_with_lnbits
 from .tasks import wait_for_cassette_state_events, wait_for_paid_invoices
 from .views import satmachineadmin_generic_router
 from .views_api import satmachineadmin_api_router
@@ -50,6 +51,12 @@ def satmachineadmin_start():
         "ext_satmachineadmin_cassette_bootstrap", wait_for_cassette_state_events
     )
     scheduled_tasks.append(cassette_task)
+    # Path-B wallet-routing hook (#20 / coord-log 2026-05-31T15:25Z):
+    # register our ATM-roster resolver with lnbits' nostr-transport so
+    # inbound kind-21000 from a known ATM npub routes to the operator's
+    # wallet, not an auto-created machine wallet. Soft-fails on lnbits
+    # versions that don't yet expose `register_roster_resolver`.
+    register_roster_with_lnbits()
 
 
 __all__ = [