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/login/system.sh

@@ -1,5 +1 @@
-run_logged $OMARCHY_INSTALL/login/sddm.sh
-if install_mode_is online; then
-  run_logged $OMARCHY_INSTALL/login/hibernation.sh
-fi
-run_logged $OMARCHY_INSTALL/login/limine-snapper.sh
+run_logged "$OMARCHY_INSTALL/login/sddm.sh"