feat: forms on TYPO3 13, loaded into the static pages with htmx

The static export replaced every EXT:form form with a contact notice. The
forms are back, rendered by TYPO3 13 and embedded in the static pages:

- Page type 1704 (/<page>/form) renders only the form plugin of a page,
  inside a .form-island element. Every form posts to that URL
  (renderingOptions.additionalParams), because on www the page URL is a
  static file that never reaches TYPO3. htmx swaps the island in place:
  validation errors, multi-step pages and confirmations. A redirect to an
  htmx request becomes HX-Redirect (HtmxRedirectMiddleware), so Redirect
  finishers send the browser to the thank-you page.
- While a request runs, an overlay with a spinner (as in MyE&P) covers
  the form. Styled inside the island: the static pages load the CSS of
  the TYPO3 10 export.
- The bw_captcha image comes from /<page>/captcha for the same reason.
  Both suffixes are in the PageType enhancer of every site with forms
  (semesterende gets one with default '' to keep its URLs).
- Ported from TYPO3 10: form setup, templates and partials, the MyE&P
  address finisher, the job application finisher with the MyE&P Team
  API client (epTeamApi* in secrets.php), the page URL/referrer finisher
  with ReferrerMiddleware (?ref=), the e-mail layout without the system
  footer, bw_captcha 5 and form_element_linked_checkbox 6. The address
  check forms are dropped.
- German language packs (EXT:form messages): availableLanguages = de,
  fetched on every deploy (typo3:language:update).
- The checkbox partials passed null to VHS' substring, which PHP 8.5
  reports as deprecated.
- DDEV no longer turns deprecations into exceptions, matching
  production: EXT:form's RenderFormValueViewHelper uses null as an array
  offset for empty optional fields (core bug, also in 13.4.37).

The static pages get their placeholders from the exporter in EP/website,
see .ddev/plans/static-export-form-islands.patch (local only).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

deploy.php

@@ -109,6 +109,7 @@ task('host:check', function () {
         'static/ep-reisen/fileadmin links there' => 'test "$(readlink -f /usr/home/eptypo3/public_html/static/ep-reisen/fileadmin)" = "$(readlink -f {{fileadmin_path}})" && echo yes',
         'free disk space' => 'df -h /usr/home/eptypo3 | tail -1',
         'secrets.php in place' => 'test -s {{deploy_path}}/shared/config/system/secrets.php && {{bin/php}} -r \'exit(is_array(require "{{deploy_path}}/shared/config/system/secrets.php") ? 0 : 1);\' && echo yes',
+        'TYPO3 translation server reachable' => 'curl -s -o /dev/null -w "%{http_code}" --max-time 10 https://localize.typo3.org/xliff/ | grep -v "^000$"',
         'MyE&P reachable' => 'curl -s -o /dev/null -w "%{http_code}" --max-time 10 https://my.ep-reisen.de/api/last-update',
     ];
     $failed = false;
@@ -152,6 +153,11 @@ task('typo3:extension:setup', function () {
     run('{{bin/php}} {{release_path}}/{{bin/typo3}} extension:setup');
 });
 
+desc('TYPO3 - German language packs (EXT:form validation messages, among others) into the release');
+task('typo3:language:update', function () {
+    run('{{bin/php}} {{release_path}}/{{bin/typo3}} language:update de --no-progress');
+});
+
 desc('TYPO3 - Clear all caches');
 task('typo3:cache:flush', function () {
     run('{{bin/php}} {{release_path}}/{{bin/typo3}} cache:flush');
@@ -179,6 +185,7 @@ task('deploy', [
     'typo3:secrets:check',
     // The schema has to exist before the new code starts serving traffic (adds and changes only).
     'typo3:extension:setup',
+    'typo3:language:update',
     // deploy:publish == deploy:symlink, deploy:unlock, deploy:cleanup, deploy:success
     'deploy:publish',
 ]);