2.0.0: Rewrite for WordPress 6.9+

Requires WordPress 6.9+ and PHP 7.4+. Updating from 1.x keeps the API credentials, all settings and the synced machines, with no reactivation needed. Shortcodes, URLs and CSS classes are unchanged.

Fixes

• Collections larger than 50 machines now sync completely; 1.x only ever fetched the first 50.
• Machine names, descriptions and image URLs are escaped (stored XSS fix).
• [mpcl] without columns no longer crashes on PHP 8.
• Emoji and other 4-byte characters are stored correctly: the table is converted to utf8mb4 on update.
• No PHP deprecation notices on PHP 8.x.

Changes

• The collection refreshes in the background via WP-Cron instead of during page views. A failing API keeps the previous copy, and visitors never see a half-updated list. Sites with DISABLE_WP_CRON need a system cron calling wp-cron.php.
• Markdown descriptions are shown as mypclist.net renders them. BBCode descriptions look as before.
• The API token is hidden on the settings page and stored encrypted. Going back to 1.x requires entering it again.
• The settings page has a "Test connection" button, and the catalogue page is chosen from a list instead of typed as an ID.
• "Entries per page" now limits the catalogue (default 100). The unused "Enable image cache" option is gone.
• Editors see a notice when an embedded machine is not synced yet; visitors see nothing.
• Deleting the plugin removes its data. Deactivating keeps everything.
• Rewritten without bundled libraries (Smarty, JBBCode, PHP connector): the package shrank from 483 KB to about 110 KB, and assets load only on pages that use the shortcode.