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.

install/preflight/migrations.sh

@@ -1,6 +1,6 @@
 OMARCHY_MIGRATIONS_STATE_PATH=~/.local/state/omarchy/migrations
 mkdir -p $OMARCHY_MIGRATIONS_STATE_PATH
 
-for file in ~/.local/share/omarchy/migrations/*.sh; do
+for file in $OMARCHY_PATH/migrations/*.sh; do
   touch "$OMARCHY_MIGRATIONS_STATE_PATH/$(basename "$file")"
 done

install/preflight/pacman.sh

@@ -3,8 +3,8 @@ if [[ -n ${OMARCHY_ONLINE_INSTALL:-} ]]; then
   omarchy-pkg-add base-devel
 
   # Configure pacman
-  sudo cp -f ~/.local/share/omarchy/default/pacman/pacman-${OMARCHY_MIRROR:-stable}.conf /etc/pacman.conf
-  sudo cp -f ~/.local/share/omarchy/default/pacman/mirrorlist-${OMARCHY_MIRROR:-stable} /etc/pacman.d/mirrorlist
+  sudo cp -f $OMARCHY_PATH/default/pacman/pacman-${OMARCHY_MIRROR:-stable}.conf /etc/pacman.conf
+  sudo cp -f $OMARCHY_PATH/default/pacman/mirrorlist-${OMARCHY_MIRROR:-stable} /etc/pacman.d/mirrorlist
 
   sudo pacman-key --recv-keys 40DFB630FF42BCFFB047046CF0134EE680CAC571 --keyserver keys.openpgp.org
   sudo pacman-key --lsign-key 40DFB630FF42BCFFB047046CF0134EE680CAC571