Regroup settings into collapsible sections

Restructure the flat settingsCategories list into five top-level groups
(General, Appearance, Screens, Productivity, Add-ons), each a collapsible
nav section with persisted open/closed state. Consolidate the six
single-toggle modern_* categories (posts/pages/media/users/comments/
plugins) into one "Content tables" screen. Search now matches on group +
category + subtitle and hides empty groups. Field definitions, save flow,
and setting keys are unchanged.

settingsConfig.js exports settingsGroups plus a flattened settingsCategories
for default-seeding and deep-link lookups.

(package-lock.json: version field synced 2.16.0 -> 3.1.0 to match package.json.)

Co-Authored-By: Claude Opus 4.8 <[email protected]>

app/package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "aurora-admin-app",
-  "version": "2.16.0",
+  "version": "3.1.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "aurora-admin-app",
-      "version": "2.16.0",
+      "version": "3.1.0",
       "dependencies": {
         "@codemirror/lang-css": "^6.3.1",
         "@codemirror/lang-html": "^6.4.11",