Permission needed to create network?

I installed virt-manager + the QEMU add-on via flathub.

When trying to create a new network, I got "operation not permitted":

```
Error creating virtual network: error creating bridge interface virbr0: Operation not permitted

Traceback (most recent call last):
File "/app/share/virt-manager/virtManager/asyncjob.py", line 67, in cb_wrapper
callback(asyncjob, *args, **kwargs)
~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/app/share/virt-manager/virtManager/createnet.py", line 427, in _async_net_create
netobj.create()
~~~~~~~~~~~~~^^
File "/app/lib/python3.13/site-packages/libvirt.py", line 3623, in create
raise libvirtError('virNetworkCreate() failed')
libvirt.libvirtError: error creating bridge interface virbr0: Operation not permitted
```

I think this is because the add-on would use a user session, right? Is there a way for the flathub version of qemu/virtmanager to use system session instead?

Start by reproducing the network-creation failure in the Flathub package and inspect the Flatpak permissions and libvirt session used. The traceback points to virtManager/createnet.py and virtManager/asyncjob.py; done means confirming whether system-session access is supported and documenting the required configuration or limitation.

Written by the indexing model from the issue text.