High-bandwidth USB webcams through virtual USB can crash the host

Passing a 4K webcam (Logitech BRIO) through QEMU's virtual USB controller caused isochronous transfer failures that cascaded into a full host crash. Lower-bandwidth cameras (1080p OBSBOT) work fine. For 4K webcams, use a dedicated PCIe USB card with controller passthrough instead.

The BRIO's video stream failed with a flood of `libusb_submit_transfer [iso]: -4 [NO_DEVICE]` errors. The device disconnected, re-enumerated on the host, triggered USB resets across all devices on the same controller, and crashed Proxmox.\n\nThe OBSBOT Meet SE (1080p, directly connected) works fine through the same virtual USB passthrough. The issue is bandwidth — 4K isochronous transfers exceed what QEMU's virtual XHCI controller can handle reliably.\n\nFix options:\n1. Use a lower-res camera (1080p works)\n2. Dedicate a PCIe USB 3.0 card to the VM via controller passthrough\n3. Don't pass through 4K webcams via virtual USB\n\nDiscovered during Windows VM setup (2026-04-13). Caused full Proxmox host crash.