feat: register transport RPCs over LNbits nostr transport

Hooks the existing withdraw CRUD into the LNbits nostr transport layer
so an HTTP-allergic client (e.g. lamassu-next ATM) can manage LNURL-
withdraw links over kind-21000 encrypted events instead of HTTP.

New `withdraw_start()` lifecycle hook (auto-invoked by the LNbits
extension manager) imports the transport's `register_rpc` and registers
four RPCs mirroring the Lightning.Pub `withdraw.*` contract exactly so
lamassu-next's adapter can be a pure name-translation layer:

  lnurlw_create_link   AUTH_WALLET
  lnurlw_get_link      AUTH_WALLET
  lnurlw_update_link   AUTH_WALLET
  lnurlw_delete_link   AUTH_WALLET

All handlers are thin shims around the existing crud.py functions —
no business logic duplication. *_get / *_update / *_delete verify
that the link's stored wallet matches the caller's wallet id.

Also registers a link-owner resolver with the core subscriptions
module (under tag "withdraw", extras-key "withdrawal_link_id" — the
exact field name views_lnurl.py:144 stamps on payment.extra when a
withdraw settles). That lets clients call
`subscribe_payments({tag:"withdraw", link_id:...})` and stream real-
time claim events without polling, with ownership enforced server-side.

The transport import is guarded by try/except ImportError so this
extension still loads cleanly against an LNbits build that doesn't
have nostr_transport.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

__init__.py

@@ -17,4 +17,46 @@ withdraw_ext.include_router(withdraw_ext_generic)
 withdraw_ext.include_router(withdraw_ext_api)
 withdraw_ext.include_router(withdraw_ext_lnurl)
 
-__all__ = ["db", "withdraw_ext", "withdraw_static_files"]
+
+def withdraw_start() -> None:
+    """
+    Register this extension's RPCs with the LNbits nostr transport so an
+    HTTP-allergic client (e.g. lamassu-next ATM) can manage LNURL-withdraw
+    links without touching the HTTP API. Also wires the link-owner
+    resolver so subscribe_payments({tag:"withdraw", link_id:...}) can
+    verify ownership.
+
+    No-op if the core transport module isn't present in the LNbits build.
+    No runtime `if nostr_transport_enabled` guard is needed — when
+    disabled, the relay pool never publishes, so registered RPCs are
+    simply unreachable.
+    """
+    try:
+        from lnbits.core.services.nostr_transport.dispatcher import (
+            AUTH_WALLET,
+            register_rpc,
+        )
+        from lnbits.core.services.nostr_transport.subscriptions import (
+            register_link_owner_resolver,
+        )
+    except ImportError:
+        return
+
+    from .transport_rpcs import (
+        handle_lnurlw_create_link,
+        handle_lnurlw_delete_link,
+        handle_lnurlw_get_link,
+        handle_lnurlw_update_link,
+        resolve_withdraw_owner,
+    )
+
+    register_rpc("lnurlw_create_link", handle_lnurlw_create_link, AUTH_WALLET)
+    register_rpc("lnurlw_get_link", handle_lnurlw_get_link, AUTH_WALLET)
+    register_rpc("lnurlw_update_link", handle_lnurlw_update_link, AUTH_WALLET)
+    register_rpc("lnurlw_delete_link", handle_lnurlw_delete_link, AUTH_WALLET)
+    register_link_owner_resolver(
+        "withdraw", resolve_withdraw_owner, link_extra_key="withdrawal_link_id"
+    )
+
+
+__all__ = ["db", "withdraw_ext", "withdraw_start", "withdraw_static_files"]