Instead of guessing the primary monitor (unreliable on Niri),
show the panel with action buttons on every monitor. All get
keyboard exclusive so the focused monitor captures input.
Also set exclusive_zone -1 to overlay Waybar, and delay
initial focus grab via GLib.idle_add for layer shell readiness.
- Replace hardcoded colors with @theme_* variables for consistency
- Card backgrounds use alpha for subtle translucency over wallpaper
- Confirmation dialog grabs focus on "No" button for safe keyboard nav
Same pattern as moonlock — re-exec the process with LD_PRELOAD
set so gtk4-layer-shell is loaded before libwayland-client.
Skipped during tests via pytest/unittest module detection.
