refactor(console): migrate one-time data converters to console commands
Replace install/*_converter.php scripts with module console commands guarded against
re-runs via OneTimeTaskTracker (config/autoload/one_time_tasks.local.php, --force to rerun).
New shared services: Johncms\Console\OneTimeTaskTracker, Johncms\Bbcode\BbcodeToHtmlConverter.
New commands: library:convert-bbcode, library:convert-comments, library:generate-slugs,
downloads:convert-bbcode, downloads:convert-comments, downloads:generate-slugs.
Update CHANGELOG and docs submodule pointer.
re-runs via OneTimeTaskTracker (config/autoload/one_time_tasks.local.php, --force to rerun).
New shared services: Johncms\Console\OneTimeTaskTracker, Johncms\Bbcode\BbcodeToHtmlConverter.
New commands: library:convert-bbcode, library:convert-comments, library:generate-slugs,
downloads:convert-bbcode, downloads:convert-comments, downloads:generate-slugs.
Update CHANGELOG and docs submodule pointer.