Make setup ISO-only

Remove legacy online installer entrypoints, collapse migrations for 4.0, and move setup responsibilities into target-side system, hardware, and user commands.

install/user/sleep-lock.sh

@@ -0,0 +1,7 @@
+mkdir -p ~/.config/systemd/user/
+cp "$OMARCHY_PATH/config/systemd/user/omarchy-sleep-lock.service" ~/.config/systemd/user/
+if declare -F omarchy_user_systemctl_enable >/dev/null; then
+  omarchy_user_systemctl_enable omarchy-sleep-lock.service
+else
+  systemctl --user enable omarchy-sleep-lock.service
+fi