Add 'websitebox' shell command as shortcut for docker compose

Installs a shell function in .bashrc/.zshrc that auto-cds into the
project directory, so users can run 'websitebox up -d' from anywhere
instead of remembering to cd first. Shows usage examples in the
installer's closing output. Setup summary updated to use the shortcut.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

setup.sh

@@ -289,7 +289,7 @@ printf "    ${GREEN}✓ Success looks like:${RESET}  ${BOLD}${SERVER_IP}${RESET}
 printf "    ${RED}✗ Not ready yet:${RESET}     ${DIM}(blank output or a different IP — wait a few minutes and try again)${RESET}\n\n"
 printf " ${BLUE}3.${RESET} ${BOLD}Launch your website${RESET}\n"
 printf "    Once DNS is working, copy this command into the server terminal:\n\n"
-printf "      ${CYAN}cd ~/websitebox && docker compose up -d${RESET}\n\n"
+printf "      ${CYAN}websitebox up -d${RESET}\n\n"
 printf " ${BLUE}4.${RESET} ${BOLD}Visit your site${RESET}\n"
 printf "    Your website:  ${CYAN}https://${DOMAIN}${RESET}\n"
 printf "    Admin login:   ${CYAN}https://${DOMAIN}/wp-admin${RESET}\n"