Add crontrol_manage_cap filter for the required capability

[Gilmoursa]

Summary

Closes #157.

Adds a crontrol_manage_cap filter so site owners can override the capability required to access WP Crontrol, without needing to hack around the menu or hook into access checks manually.

The most common use case is multisite installs where manage_options is too permissive — standard site admins have it, but the site owner only wants network admins (who have manage_network_options) to see and use the plugin.

Usage

add_filter( 'crontrol_manage_cap', function( string $cap ): string {
    return 'manage_network_options';
} );

Implementation

• Added get_manage_cap() helper function in bootstrap.php that applies the filter and defaults to 'manage_options'
• Replaced all 13 hardcoded 'manage_options' capability strings in bootstrap.php (action handlers + menu registration) with get_manage_cap()
• Updated WordPressUserContext to call \Crontrol\get_manage_cap() for the same consistency

The edit_files capability used for PHP cron events is unchanged — that one is tied to WordPress core's own "can this user edit PHP files" concept and is separate from the general management cap.

Test plan

• Default behaviour unchanged — manage_options users can access everything as before
• With the filter returning manage_network_options, standard site admins can no longer see the Cron Events or Cron Schedules menu items
• With the filter returning manage_network_options, standard site admins get a wp_die() if they attempt to POST to any crontrol action directly

[johnbillion]

Thanks for the PR @Gilmoursa, I appreciate it, but I'll close this in favour of the existing PR at #190 which implements fine-grained capabilities for each of the actions in WP Crontrol. That approach means capabilities can be granted to and denied from users and roles directly without having to use filters.

Cheers.

[Gilmoursa]

Thanks for the context, that makes sense! The fine-grained capabilities approach in #190 is a much better solution for users. Looking forward to seeing it land. Cheers!