feat(links): move friend links to native WordPress links with review flow

- enable the native Links manager and drop the custom friend-link option/REST path
- add per-page link settings for the friends template
- render link categories from get_bookmarks() with search and page-content options
- add a validated public link submission endpoint with logo upload, captcha, rate limiting and duplicate checks
- create pending links for review and notify administrators by email and in-app message
- add native Links admin pending count, columns and edit notes
- cover the new submission and cleanup contracts

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/Settings/DisplayPageGroups.php

@@ -189,7 +189,6 @@ trait DisplayPageGroups {
             'tabbar'                      => self::get_footer_tabbar_settings(),
             'floating_buttons'            => self::get_floating_buttons_settings(),
             'header_theme'                => self::get_header_theme_config(),
-            'friend_links'                => self::get_friend_links(),
             'cms_features'                => self::get_cms_features(),
             'page_display'                => self::get_page_display_settings(),
             'footer_theme'                => self::get_footer_theme_config(),