refactor: complete addon harmonization (filebrowser-quantum, glances, olivetin, phpmyadmin, coder-code-server polish)

- Remove local get_lxc_ip() shadow in glances.sh, use core.func version
- Fix double header_info() call in olivetin.sh with _HEADER_SHOWN reset
- Add core.func/tools.func/error_handler.func sourcing to phpmyadmin.sh
- Replace unsafe hostname -I fallback with get_lxc_ip everywhere
- Use $STD for command execution and shared msg_info/msg_ok/msg_error/msg_warn
- All files verified clean via shellcheck (only expected SC1090 noise)

tools/addon/coder-code-server.sh

@@ -69,7 +69,7 @@ rm -rf code-server_"${VERSION}"_amd64.deb
 mkdir -p "${HOME}/.config/code-server/"
 
 if [ "$preexisting_config" = false ]; then
-cat <<EOF >"$config_path"
+  cat <<EOF >"$config_path"
 bind-addr: 0.0.0.0:8680
 auth: none
 password: