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

config/sites/vitec/config.yaml

@@ -24,6 +24,7 @@ dependencies:
   - apache-solr-for-typo3/solr-open-search
   - apache-solr-for-typo3/solr-stylesheets
   - apache-solr-for-typo3/solr-bootstrap-css
+  - evomedien/megamenu
 frontendBase: ''
 headless: 1
 languages:

config/sites/vitec/settings.yaml

@@ -2,3 +2,4 @@ vitec.debugMode: true
 my.example.setting: Test
 menu.footer.pageUids: '1,2,3'
 menu.meta.pageUids: '5'
+megamenu.contentUid: 10366