feat(tools): add root-ssh-login tool to enable or disable root SSH password login

- add tools/root-ssh-login.sh with interactive menu, --enable/--disable/--status flags, and sshd drop-in config management
- register root-ssh-login in lxs.sh dispatch and tools/index.sh interactive menu
- document new tool in README.md command reference and project structure

lxs.sh

@@ -289,6 +289,7 @@ cmd_tool() {
         harden)    download_and_run "tools/harden.sh" "$@" ;;
         root-password) download_and_run "tools/root-password.sh" "$@" ;;
         update)    download_and_run "tools/update-server.sh" "$@" ;;
+        root-ssh-login) download_and_run "tools/root-ssh-login.sh" "$@" ;;
         "")        echo -e "${RED}[✗] Missing tool name. Try: lxs help${NC}"; return 1 ;;
         *)         echo -e "${RED}[✗] Unknown tool: $tool. Try: lxs help${NC}"; return 1 ;;
     esac