1.3.3 – Fix plugin page link localization

Bug fixes

• Plugin page link not translated: the "Manage notifications" link in the YOURLS plugin list remained in English even with YOURLS set to Italian, because yourls_register_plugin_page() was called before ynm_load_textdomain() — the textdomain was not yet loaded when the string was evaluated. Moved ynm_load_textdomain() to the top of ynm_boot(), before any use of yourls__().
• "Back to top" footer link not translated: the string was hardcoded instead of wrapped in yourls__(). Italian translation: "Torna all'inizio".