Translate pages, areas, menus, forms and posts field by field instead of rebuilding them

A site can have further languages (Settings → Languages). A page is built once; each language
adds only its texts, keyed by the stable block IDs, plus its own address under /en/… (ADR 111,
document schema v27, migration 20261009000100 for page_translation).

- Editor: DE | EN switch, a list of all texts with original, state (missing, translated,
  original changed) and filter; structure stays with the main language. Undo, drafts,
  publishing and revisions cover all languages at once.
- Website: /en and translated slugs, lang, canonical, hreflang with x-default, og:locale,
  sitemap; links to translated pages follow the language; a language switch block.
- Header, footer and linked sections translate the same way; menu entries carry labels per
  language; fixed template texts come from a small dictionary.
- Forms: labels, help, options, button and success message per language; messages and the
  step script speak the language, the submission and the email stay in the main language.
- Posts, archives, category names, consent text and the 404 page follow the language.
- Single-language sites see none of it and never touch the new table.

The forms administration becomes an overview with one row per form and its own edit page;
fields are one line each with details collapsed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/EditorSecurityTest.php

@@ -681,8 +681,12 @@ final class EditorSecurityTest extends WebTestCase
         preg_match('#<style>(.*?)</style>#s', $html, $style);
         self::assertStringContainsString("'sha256-".base64_encode(hash('sha256', $style[1], true))."'", (string) $client->getResponse()->headers->get('Content-Security-Policy'));
 
-        // Eine Farbe, die keine ist, wird mit Meldung abgelehnt und nichts geaendert.
+        // Die Übersicht listet das Formular, bearbeitet wird es auf seiner eigenen Seite.
         $crawler = $client->request('GET', '/admin/forms');
+        self::assertSame(0, $crawler->filter('.form-def')->count(), 'Die Übersicht zeigt keine Editoren.');
+        self::assertSame('/admin/forms/kontakt', $crawler->filter('.form-list a')->first()->attr('href'));
+        // Eine Farbe, die keine ist, wird mit Meldung abgelehnt und nichts geaendert.
+        $crawler = $client->request('GET', '/admin/forms/kontakt');
         $token = $crawler->filter('.form-def input[name="_csrf_token"]')->first()->attr('value');
         self::assertCount(5, $crawler->filter('.form-def')->first()->filter('.field-card:not(.field-card-new)'), 'Jedes Feld ist eine Karte.');
         self::assertSame('Anfrage senden', $crawler->filter('.form-def')->first()->filter('[data-preview-button]')->text());
@@ -696,7 +700,7 @@ final class EditorSecurityTest extends WebTestCase
     public function testFormAdministrationNeedsAPublisherRoleAndACsrfToken(): void
     {
         $client = $this->login('publisher');
-        $crawler = $client->request('GET', '/admin/forms');
+        $crawler = $client->request('GET', '/admin/forms/neu');
         self::assertResponseIsSuccessful();
         $token = $crawler->filter('.form-def input[name="_csrf_token"]')->first()->attr('value');
         $field = ['fields' => [['name' => 'email', 'type' => 'email', 'label' => 'E-Mail', 'required' => '1']]];