fix: audit LOW fixes — nmcli guards, sink cancel, cpugov stderr, gpu interval

- moonarch-vpn: add `--` argument-terminator to `nmcli connection up/down`
  so a profile name starting with `-` is never interpreted as a flag.
- moonarch-sink-switcher: guard against empty `$sink` when walker is
  cancelled, since awk masks walker's non-zero exit. Prevents the error
  `pactl set-default-sink ""` on every dismissal.
- moonarch-waybar-cpugov: redirect stderr so non-cpufreq systems (VMs,
  some desktops) do not spam the journal on every 60s poll.
- waybar config: switch custom/gpu-usage from `restart-interval: 10` to
  `interval: 60`. The module lives in a closed drawer, a 10 s poll spawn
  was unnecessary background noise.

defaults/bin/moonarch-waybar-cpugov

@@ -2,7 +2,7 @@
 # ABOUTME: Waybar-Modul das den CPU-Governor als JSON ausgibt.
 # ABOUTME: Wird von der Waybar custom/cpugov Config referenziert.
 
-CPU_GOV=$(cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor)
+CPU_GOV=$(cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_governor 2>/dev/null)
 
 case $CPU_GOV in
   performance)