Add evo_megamenu_json extension and seed the megamenu

- new project-neutral extension evo_megamenu_json (Evomedien): a Megamenu
  plugin holding entries, columns, items, teaser cards and a featured slot
  as nested records; presentation settings travel with the payload so the
  front end reads behaviour instead of hard-coding it; published as
  page.10.fields.megaMenu, driven by the site settings megamenu.contentUid
  and megamenu.storagePid
- vitec:seed-megamenu fills one element from the live structure: 5 entries,
  26 columns, 95 items, 4 story cards; items without a page yet are flagged
  pending so the front end falls back to the column link
- vitec:debug-sets prints the resolved site set order
- read-only diagnostics: check_megamenu_schema.php, check_typoscript_templates.php
- docs: schema updates run via extension:setup (database:updateschema no
  longer exists in v14), and a JSON Accept header activates headless-mixed,
  which strips every set-added page field

packages/evo_megamenu_json/ext_emconf.php

@@ -0,0 +1,21 @@
+<?php
+
+$EM_CONF[$_EXTKEY] = [
+    'title' => 'EVO Megamenu JSON',
+    'description' => 'Editable megamenu for headless TYPO3: one plugin fills columns, teaser cards and a featured slot; the menu is delivered as JSON.',
+    'category' => 'plugin',
+    'author' => 'Evomedien',
+    'author_email' => '',
+    'state' => 'stable',
+    'clearCacheOnLoad' => 1,
+    'version' => '1.0.0',
+    'constraints' => [
+        'depends' => [
+            'typo3' => '13.4.0-14.9.99',
+        ],
+        'conflicts' => [],
+        'suggests' => [
+            'headless' => '',
+        ],
+    ],
+];