Normalize hard-coded ~/.local/share/omarchy refs to $OMARCHY_PATH

The package-installed paths live at /usr/share/omarchy; the script-install
paths live at ~/.local/share/omarchy. $OMARCHY_PATH is set by install.sh
during the install flow and by /etc/profile.d/omarchy.sh in package mode.
Scripts that hard-code the script-install path don't honour that and will
misbehave once shipped to /usr/bin.

16 files migrated via sed s|~/\.local/share/omarchy|$OMARCHY_PATH|g
and s|$HOME/\.local/share/omarchy|$OMARCHY_PATH|g:

bin/:
- omarchy-plymouth-{preview,reset,set}
- omarchy-refresh-{limine,plymouth}
- omarchy-reinstall-configs
- omarchy-show-logo
- omarchy-games-retro-install
- omarchy-install-gaming-battlenet

install/:
- config/branding.sh
- packaging/{fonts,icons}.sh
- post-install/{finished,pacman}.sh
- preflight/{migrations,pacman}.sh

Deliberately NOT migrated:
- bin/omarchy-dev-add-migration: uses 'cd ~/.local/share/omarchy' to
  resolve a git repo for 'git log'. The packaged binary doesn't have a
  git repo to read; this command only makes sense in dev mode where
  the home path is the right one.
- bin/omarchy-install-browser:69: writes a string into a chromium
  config file that chromium itself interprets; not a bash-resolved path.
- install/helpers/errors.sh:125: the boot.sh-style relaunch behaviour
  needs a separate redesign.

bin/omarchy-plymouth-reset

@@ -5,7 +5,7 @@
 
 theme_dir="/usr/share/plymouth/themes/omarchy"
 
-sudo find ~/.local/share/omarchy/default/plymouth -maxdepth 1 -type f -exec cp -t "$theme_dir/" {} +
+sudo find $OMARCHY_PATH/default/plymouth -maxdepth 1 -type f -exec cp -t "$theme_dir/" {} +
 sudo plymouth-set-default-theme omarchy
 
 if omarchy-cmd-present limine-mkinitcpio; then