Add a real replacement Posts management page (v2.5.0)

Posts was previously just dark-themed skinning over the native
edit.php list table, unlike Comments/Plugins which are genuine
replacements. Built the same way: new PostsData.php REST controller
(list with status/search filters matching native tabs, trash, restore,
permanent delete) and a Vue page matching the Comments layout.

- SubApps.php registers it as aurora-admin-posts, parented under
  edit.php (same pattern as Plugins under plugins.php).
- redirect_native_pages() redirects direct edit.php visits (typed URL,
  not just the sidebar link) to the Aurora page — gated to the default
  post type only, so Pages and other custom post types are untouched.
- MenuSerializer rewrites the sidebar's Posts/All Posts links the same
  way Plugins/Comments already were.
- Gated by Settings > Posts' "Modern posts table" toggle, re-added now
  that it has a real implementation (it was removed a few commits ago
  for describing a feature that didn't exist).
- Fixed modern_plugins/modern_comments/modern_posts all defaulting to
  visually "on" in the Settings UI to match their actual PHP default.

Verified live: trash/restore/status filters/search all work correctly,
edit.php redirects to the Aurora page, edit.php?post_type=page (Pages)
correctly does not.

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

app/src/pages/settings/settingsConfig.js

@@ -152,6 +152,21 @@ export const settingsCategories = [
       },
     ],
   },
+  {
+    id: 'posts',
+    title: 'Posts',
+    subtitle: 'Post management and display preferences',
+    icon: 'dashicons-admin-post',
+    fields: [
+      {
+        key: 'modern_posts',
+        type: 'toggle',
+        label: 'Modern posts table',
+        description: 'Use the Aurora posts management interface.',
+        default: true,
+      },
+    ],
+  },
   {
     id: 'plugins',
     title: 'Plugins',
@@ -163,6 +178,7 @@ export const settingsCategories = [
         type: 'toggle',
         label: 'Modern plugins page',
         description: 'Use the Aurora plugins management interface.',
+        default: true,
       },
     ],
   },
@@ -227,6 +243,7 @@ export const settingsCategories = [
         type: 'toggle',
         label: 'Modern comments page',
         description: 'Use the Aurora comments management interface.',
+        default: true,
       },
     ],
   },