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-install-gaming-battlenet

@@ -64,9 +64,9 @@ EOF
 fi
 
 mkdir -p "$HOME/.local/share/applications" "$HOME/.local/share/icons/hicolor/48x48/apps"
-install -m 644 "$HOME/.local/share/omarchy/applications/battlenet.desktop" \
+install -m 644 "$OMARCHY_PATH/applications/battlenet.desktop" \
   "$HOME/.local/share/applications/battlenet.desktop"
-install -m 644 "$HOME/.local/share/omarchy/applications/icons/Battle.net.png" \
+install -m 644 "$OMARCHY_PATH/applications/icons/Battle.net.png" \
   "$HOME/.local/share/icons/hicolor/48x48/apps/Battle.net.png"
 gtk-update-icon-cache "$HOME/.local/share/icons/hicolor" &>/dev/null || true
 update-desktop-database "$HOME/.local/share/applications" 2>/dev/null || true