fix(packaging): autoload vhci-hcd and open its attach files for the usbip Deck pad

Steam Input only adopts the virtual Steam Deck controller when it arrives as
a real USB device (raw_gadget or usbip/vhci transports); the UHID fallback
has no USB interface and Steam ignores it. On a stock host neither
precondition for usbip held: vhci-hcd isn't loaded, and its sysfs
attach/detach files are root-only while the host runs as a user service —
so every session silently fell back to UHID and 'no controller appears on
the host' (live-debugged 2026-07-08: client events all arrived, the pad
existed, Steam just refused it).

Ship both preconditions with the host packages:
 * modules-load.d/punktfunk.conf loads vhci-hcd at boot (rpm/deb/arch;
   Bazzite gets it via the RPM payload + a modprobe in the sysext
   post-merge hook)
 * a udev rule in 60-punktfunk.rules grants the input group write on
   vhci_hcd's attach/detach whenever the device appears

Verified end-to-end on a live host: usbip in-process attach, hid-steam
binds all three interfaces, 'Steam Deck' + motion evdev appear, and Steam
adopts the pad (client-mode grab + its own virtual X360 emission).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packaging/arch/PKGBUILD

@@ -98,6 +98,8 @@ package_punktfunk-host() {
   install -Dm0755 "$T/punktfunk-host"                 "$pkgdir/usr/bin/punktfunk-host"
   # /dev/uinput + /dev/uhid -> input group (virtual gamepads + DualSense UHID)
   install -Dm0644 "$R/scripts/60-punktfunk.rules"     "$pkgdir/usr/lib/udev/rules.d/60-punktfunk.rules"
+  # vhci-hcd autoload — usbip transport for the virtual Steam Deck pad (Steam only adopts USB pads)
+  install -Dm0644 "$R/scripts/punktfunk-modules.conf" "$pkgdir/usr/lib/modules-load.d/punktfunk.conf"
   # 32 MB UDP socket buffers (send-side headroom at high bitrate)
   install -Dm0644 "$R/scripts/99-punktfunk-net.conf"  "$pkgdir/usr/lib/sysctl.d/99-punktfunk-net.conf"
   # systemd USER units (the host runs in the graphical session, not as root); repoint ExecStart.