refactor(battery): consolidate button styles, refactor service, remove ddcutil

- Merge game-mode/charge-limit CSS into shared selectors
- Rewrite Battery service with IntEnum states and charge-limit support
- Add ChargeLimitButton with active-state styling
- Drop ddcutil from dependencies (unused)

install.sh

@@ -66,7 +66,6 @@ PACKAGES=(
     acpi
     brightnessctl
     power-profiles-daemon
-    ddcutil
     at-spi2-core
     networkmanager
     network-manager-applet