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]>

app/src/shell/components/Sidebar.vue

@@ -185,6 +185,9 @@ const isAuroraActive = (item) => normalize(item.url) === current.value;
             :class="{ 'sidebar__sublink--active': isAuroraActive(item) }"
           >
             {{ item.title }}
+            <span v-if="item.locked" class="sidebar__pro-badge" title="Pro feature">
+              <span class="dashicons dashicons-lock" />
+            </span>
           </a>
         </li>
       </ul>
@@ -382,6 +385,18 @@ const isAuroraActive = (item) => normalize(item.url) === current.value;
   font-weight: 600;
 }
 
+.sidebar__pro-badge {
+  display: flex;
+  align-items: center;
+  color: var(--aurora-text-muted);
+  flex-shrink: 0;
+}
+.sidebar__pro-badge .dashicons {
+  font-size: 13px;
+  width: 13px;
+  height: 13px;
+}
+
 /* --- Aurora branded nav (right under the native menu's own divider) ---- */
 .sidebar__aurora {
   padding-bottom: 4px;