feat: NVIDIA PRIME, audio fix, timezone, dmesg error cleanup

- Add nvidia/nvidia-dkms/nvidia-libs-32bit/nvidia-vaapi-driver to niri
  live and installed profiles; wireless-regdb and sof-firmware to all
  profiles (fixes regulatory.db and SOF firmware dmesg errors)

- iso/postsetup-nvidia.sh: new mklive -x hook that re-runs dracut inside
  the rootfs chroot after the overlay is applied; ensures the squashfs
  initramfs includes nvidia.ko and omits nouveau.ko at build time —
  no driver install needed at runtime (fixes /run tmpfs overflow that was
  killing wireplumber by corrupting D-Bus sockets)

- Both ISO inner build scripts gain -x postsetup-nvidia.sh and the nonfree
  repo flag so nvidia packages resolve correctly

- niri config: wireplumber started via supervisor loop (waits for PipeWire
  socket, auto-restarts on crash) replacing the one-shot exec — survives
  any D-Bus or pipewire disruption

- build-niri-live-iso.sh: NVIDIA modprobe blacklist-nouveau.conf,
  btusb-quirks.conf, modules-load.d/nvidia.conf, dracut/10-nvidia.conf,
  Xorg intel/nvidia configs, prime-run helper, elogind run script loop
  guard, timezone Europe/Zurich overlay, updated BOOT_CMDLINE

- build-live-iso.sh: same NVIDIA + timezone + sound udev rule overlays;
  live-setup.sh timezone and audio group fix

- installer/lib/grub.sh: GRUB_CMDLINE_LINUX_DEFAULT gains
  nvidia-drm.modeset=1 rd.driver.blacklist=nouveau btusb.enable_autosuspend=0

- installer/lib/postinstall.sh: configure_nvidia_prime() adds
  blacklist-nouveau.conf, btusb-quirks.conf, dracut omit_drivers nouveau,
  modules-load.d with all four nvidia modules

config/profiles/stable-cinnamon/packages.live-desktop.list

@@ -47,6 +47,7 @@ openssh
 iwd
 wpa_supplicant
 chrony
+wireless-regdb
 
 # --- audio ---
 pipewire
@@ -54,6 +55,7 @@ wireplumber
 alsa-pipewire
 pavucontrol
 alsa-utils
+sof-firmware
 
 # --- graphics / xorg ---
 xorg-minimal