[ironrdp-client] Wire up RDPEUSB with libusb backend

[CBenoit]

Integrate the RDPEUSB client into ironrdp-client as a working demonstration. A user should be able to redirect a local USB device to an RDP server.

Depends on:

• [ironrdp-dvc] Support multiple DVC channel instances with the same name #1135
• [ironrdp-rdpeusb] Client-side protocol state machine #1137
• [ironrdp-rdpeusb] Client libusb backend (rusb) #1139

Tasks

• Add --usb-device <VID:PID | BUS:ADDR | all> CLI flag to ironrdp-client
• Wire UrbdrcListener into DrdynvcClient using the new with_listener() API
• Connect RusbBackend to the listener; handle device plug/unplug events from a background thread feeding ADD_VIRTUAL_CHANNEL / RETRACT_DEVICE into the session
• Graceful error reporting when a device is busy or access is denied (e.g. no udev rules on Linux)

Acceptance criteria

• ironrdp-client --usb-device 1234:5678 successfully redirects a USB device into an RDP session on a Windows server
• Device appears in Device Manager on the server
• Hot-plug: plugging a device mid-session works; unplugging cleans up without crashing