- app submenus return 75 on back/exit instead of 0
- index menus capture child exit code and skip pause when rc is 75
- applies to apps (coolify, pterodactyl, uptime-kuma, cloudpanel, proxmox) and tools (server-benchmark, system-infos) indexes
- move apps menu from inline lxs.sh function to apps/index.sh
- add tools/index.sh as entry point for tools menu
- rename system-tools.sh to system-infos.sh
- simplify help text to point users to the interactive menu
- update README directory tree to reflect new structure