Replace ~/.local/share/omarchy runtime paths with $OMARCHY_PATH

The git-era flow installed Omarchy to ~/.local/share/omarchy. In the
package-based flow it lives at /usr/share/omarchy (or, in dev mode, at
the path /etc/omarchy.conf's OMARCHY_PATH points at). Files that hard-
coded the old path broke on package installs:

- default/bash/rc: sourced ~/.local/share/omarchy/default/bash/*, so a
  fresh user's terminal logged ENOENT for every line. Now sources from
  $OMARCHY_PATH with /usr/share/omarchy as the safe default if the var
  is unset.

- config/systemd/user/omarchy-recover-internal-monitor.service:
  ExecStart pointed at %h/.local/share/omarchy/bin/. The script ships
  to /usr/bin via the omarchy-installer package; point straight there.

- install/config/xcompose.sh: wrote an XCompose include line pointing
  at the user-home path; use /usr/share/omarchy/ directly.

- default/hypr/paths.lua and config/hypr/hyprland.lua: fallback when
  OMARCHY_PATH is unset is /usr/share/omarchy, not the home path.

Dev-only scripts (omarchy-dev-add-migration, omarchy-reinstall-git) and
the SKILL.md docs still reference the old path; those are separate
cleanups since they don't affect a fresh install's runtime.

default/bash/rc

@@ -1,6 +1,7 @@
-source ~/.local/share/omarchy/default/bash/envs
-source ~/.local/share/omarchy/default/bash/shell
-source ~/.local/share/omarchy/default/bash/aliases
-source ~/.local/share/omarchy/default/bash/functions
-source ~/.local/share/omarchy/default/bash/init
-[[ $- == *i* ]] && bind -f ~/.local/share/omarchy/default/bash/inputrc
+: "${OMARCHY_PATH:=/usr/share/omarchy}"
+source "$OMARCHY_PATH/default/bash/envs"
+source "$OMARCHY_PATH/default/bash/shell"
+source "$OMARCHY_PATH/default/bash/aliases"
+source "$OMARCHY_PATH/default/bash/functions"
+source "$OMARCHY_PATH/default/bash/init"
+[[ $- == *i* ]] && bind -f "$OMARCHY_PATH/default/bash/inputrc"