verification failed

using version 8.0.4, verification failed with the following error

```
Traceback (most recent call last):
File "/home/user/app/.venv/lib/python3.12/site-packages/matrix_commander/matrix_commander.py", line 1248, in to_device_callback
"transaction_id": event.transaction_id,
^^^^^^^^^^^^^^^^^^^^
AttributeError: 'UnknownToDeviceEvent' object has no attribute 'transaction_id'
```

I fixed this by replacing

```
sas = client.key_verifications[event.transaction_id]

done_message = ToDeviceMessage(
type="m.key.verification.done",
recipient=event.sender,
recipient_device=sas.other_olm_device.device_id,
content={
"transaction_id": event.transaction_id,
},
)
```

with

```
sas = client.key_verifications[event.source['content']['transaction_id']]

done_message = ToDeviceMessage(
type="m.key.verification.done",
recipient=event.sender,
recipient_device=sas.other_olm_device.device_id,
content={
"transaction_id": event.source['content']['transaction_id'],
},
)
```

The issue is in matrix_commander.py line 1248 where an UnknownToDeviceEvent lacks a transaction_id attribute. Look at the to_device_callback function and the event object structure. The fix accesses event.source['content']['transaction_id'] instead. Test by running the verification flow to ensure the error is resolved.

Scritto dal modello di indicizzazione a partire dal testo della issue.