Add free/paid feature gating (Role Editor, Activity Log, DB Explorer,

Analytics, White Label, remote site switcher are paid)

- New License class is the single gate every paid feature checks —
  today it's a placeholder (any non-empty license_key counts as active)
  since there's no license server yet, but every gated feature already
  funnels through it so swapping in real remote validation later won't
  touch anything else.
- Role Editor, Activity Log, and Database Explorer stay registered/
  capability-checked as before, but render an UpgradeNotice screen
  instead of the real feature when unlicensed (and skip loading the
  real JS bundle/REST data). Menu Creator, Admin Notices, Comments,
  and Plugins stay free.
- Analytics' tracking hooks and REST endpoint, and White Label's
  favicon/rename/text-replace hooks, simply don't register without a
  license. Settings fields for both stay visible/editable either way.
- Remote site switcher gated alongside its existing capability check.
- Sidebar shows a small lock badge on locked Aurora nav items; the
  Dashboard's Analytics tab shows the same upgrade prompt when locked.
- Fixed an unrelated bug surfaced while testing Role Editor: RolesData's
  REST callback called get_editable_roles() without loading
  wp-admin/includes/user.php first, which REST requests don't get for
  free (only real wp-admin page loads do) — 500'd every time.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

admin/src/Rest/AnalyticsData.php

@@ -2,6 +2,7 @@
 namespace AuroraAdmin\Rest;
 
 use AuroraAdmin\Analytics\Analytics;
+use AuroraAdmin\Licensing\License;
 
 defined("ABSPATH") || exit();
 
@@ -22,7 +23,7 @@ class AnalyticsData
       "methods" => "GET",
       "callback" => [self::class, "handle"],
       "permission_callback" => function () {
-        return current_user_can("read");
+        return current_user_can("read") && License::is_feature_available("analytics");
       },
     ]);
   }