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]>

config/system/additional.php

@@ -35,8 +35,11 @@ if (getenv('IS_DDEV_PROJECT') == 'true') {
                 'trustedHostsPattern' => '.*.*',
                 'devIPmask' => '*',
                 'displayErrors' => 1,
-                // Warnings and deprecations are exceptions locally: they are how PHP 7.4 leftovers show up
-                'exceptionalErrors' => 12290,
+                // Warnings are exceptions locally: they are how PHP 7.4 leftovers show up. Deprecations
+                // are not (production neither): PHP 8.5 deprecations in vendor code, e.g. EXT:form's
+                // RenderFormValueViewHelper, would break requests that work in production. They are
+                // still written to the deprecation log.
+                'exceptionalErrors' => E_WARNING | E_RECOVERABLE_ERROR,
             ],
             'BE' => [
                 'debug' => true,