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>

transport_rpcs.py

@@ -0,0 +1,119 @@
+"""
+Nostr-transport RPC handlers for the withdraw (LNURL-withdraw) extension.
+
+Names mirror the Lightning.Pub `withdraw.*` contract that the lamassu-next
+ATM consumes (see ~/dev/shocknet/lamassu-next/packages/lightning/src/client.ts
+lines ~301–351). That keeps the lamassu-next-side adapter a pure name
+translation — no semantic reshaping.
+
+Auth model (set in `__init__.py:withdraw_start`):
+- create / get / update / delete  → AUTH_WALLET; the calling pubkey must
+  own the wallet the link is scoped to. *_get / *_update / *_delete also
+  verify the link's stored `wallet` matches the caller's wallet id.
+
+`resolve_withdraw_owner` is registered with the core subscription module
+under tag `"withdraw"` and extras-key `"withdrawal_link_id"` (matching
+where the extension stamps the link id on settlement — see
+`views_lnurl.py:144`). That lets `subscribe_payments({tag:"withdraw",
+link_id:...})` enforce ownership without core importing this module.
+"""
+
+from __future__ import annotations
+
+from lnbits.core.models.wallets import WalletTypeInfo
+from lnbits.core.services.nostr_transport.models import NostrRpcRequest
+
+from .crud import (
+    create_withdraw_link,
+    delete_withdraw_link,
+    get_withdraw_link,
+    update_withdraw_link,
+)
+from .models import CreateWithdrawData
+
+
+async def handle_lnurlw_create_link(
+    auth: WalletTypeInfo, request: NostrRpcRequest
+) -> dict:
+    body = request.body or {}
+    data = CreateWithdrawData(**body)
+    link = await create_withdraw_link(data, auth.wallet.id)
+    return _to_dict(link)
+
+
+async def handle_lnurlw_get_link(
+    auth: WalletTypeInfo, request: NostrRpcRequest
+) -> dict:
+    link_id = _require_id(request)
+    link = await _require_owned_link(link_id, auth.wallet.id)
+    return _to_dict(link)
+
+
+async def handle_lnurlw_update_link(
+    auth: WalletTypeInfo, request: NostrRpcRequest
+) -> dict:
+    link_id = _require_id(request)
+    link = await _require_owned_link(link_id, auth.wallet.id)
+    body = request.body or {}
+    _MUTABLE = {
+        "title",
+        "min_withdrawable",
+        "max_withdrawable",
+        "uses",
+        "wait_time",
+        "is_unique",
+        "webhook_url",
+        "webhook_headers",
+        "webhook_body",
+        "custom_url",
+        "enabled",
+    }
+    for k, v in body.items():
+        if k in _MUTABLE:
+            setattr(link, k, v)
+    updated = await update_withdraw_link(link)
+    return _to_dict(updated)
+
+
+async def handle_lnurlw_delete_link(
+    auth: WalletTypeInfo, request: NostrRpcRequest
+) -> dict:
+    link_id = _require_id(request)
+    await _require_owned_link(link_id, auth.wallet.id)
+    await delete_withdraw_link(link_id)
+    return {"ok": True}
+
+
+async def resolve_withdraw_owner(link_id: str) -> str | None:
+    """For the core subscription module: link_id -> wallet_id (or None)."""
+    link = await get_withdraw_link(link_id)
+    return link.wallet if link else None
+
+
+# ---------------------------------------------------------------------------
+# helpers
+# ---------------------------------------------------------------------------
+
+
+def _require_id(request: NostrRpcRequest) -> str:
+    body = request.body or {}
+    link_id = body.get("id")
+    if not link_id:
+        raise ValueError("withdraw: body.id is required")
+    return str(link_id)
+
+
+async def _require_owned_link(link_id: str, wallet_id: str):
+    link = await get_withdraw_link(link_id)
+    if link is None:
+        raise ValueError(f"withdraw: link not found: {link_id}")
+    if link.wallet != wallet_id:
+        raise PermissionError(
+            "withdraw: link does not belong to caller's wallet"
+        )
+    return link
+
+
+def _to_dict(link) -> dict:
+    import json
+    return json.loads(link.json())