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

iso/_inner-build-niri-live.sh

@@ -221,6 +221,7 @@ trap _cleanup_mklive_builds EXIT
     -T "$ISO_TITLE" \
     -p "$ISO_PKGS" \
     -I "$INCLUDE_DIR" \
+    -x "$PROJECT_DIR/iso/postsetup-nvidia.sh" \
     -C "${BOOT_CMDLINE:-}" \
     -o "$OUT_ISO"