Fixes exception in lookup_invoice:
```
62.69 | E | plugins.nwc.nwcserver.NWCServer | Error handling nwc request
Traceback (most recent call last):
File "/home/user/code/vibecoding_vm/electrum/electrum/plugins/nwc/nwcserver.py", line 381, in run_request_task
await task
File "/home/user/code/vibecoding_vm/electrum/electrum/util.py", line 1211, in wrapper
return await func(*args, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/user/code/vibecoding_vm/electrum/electrum/plugins/nwc/nwcserver.py", line 526, in handle_lookup_invoice
info = self.wallet.lnworker.get_payment_info(invoice.payment_hash, direction=RECEIVED)
^^^^^^^^^^^^^^^^^^^^
AttributeError: 'Invoice' object has no attribute 'payment_hash'
```
Always includes bolt11 invoice in response, even if the client already
sent it to us in the request. It doesn't seem useful and is marked
optional in the spec but https://sandbox.albylabs.com considers the
response invalid if the invoice is not included.
f321x
f64923b472
