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>

templates/admin/editor.html.twig

@@ -22,6 +22,8 @@
             <button type="button" data-viewport="tablet" aria-pressed="false" title="Tablet"><svg viewBox="0 0 24 24" aria-hidden="true"><rect x="4" y="2" width="16" height="20" rx="2"/><path d="M11 18h2"/></svg><span>Tablet</span></button>
             <button type="button" data-viewport="mobile" aria-pressed="false" title="Mobil"><svg viewBox="0 0 24 24" aria-hidden="true"><rect x="7" y="2" width="10" height="20" rx="2"/><path d="M11 18h2"/></svg><span>Mobil</span></button>
         </div>
+        {# Der Sprachumschalter (ADR 111). Er erscheint nur, wenn die Website weitere Sprachen hat. #}
+        <div id="language-switch" class="language-switch" role="group" aria-label="Sprache der Bearbeitung" hidden></div>
         <div class="history-actions">
             <button id="undo" class="icon-button" title="Rückgängig (Strg+Z)" aria-label="Rückgängig" disabled><svg viewBox="0 0 24 24" aria-hidden="true"><path d="M9 14 4 9l5-5"/><path d="M4 9h10a6 6 0 0 1 0 12h-3"/></svg></button>
             <button id="redo" class="icon-button" title="Wiederholen (Strg+Umschalt+Z)" aria-label="Wiederholen" disabled><svg viewBox="0 0 24 24" aria-hidden="true"><path d="m15 14 5-5-5-5"/><path d="M20 9H10a6 6 0 0 0 0 12h3"/></svg></button>
@@ -71,6 +73,7 @@
                     <div class="tree-tools"><button id="expand-all" class="text-button" type="button">Alle öffnen</button><button id="collapse-all" class="text-button" type="button">Einklappen</button><button id="nest" class="text-button" type="button" title="In vorherigen Container verschachteln">⇥ Einrücken</button><button id="outdent" class="text-button" type="button" title="Eine Ebene herausheben">⇤ Ausrücken</button></div>
                     <nav id="structure" aria-label="Blöcke auswählen"></nav>
                 </section>
+                <section class="sidebar-view" data-view="translate" id="translate-panel" aria-label="Übersetzung" hidden></section>
                 <section class="sidebar-view" data-view="element" hidden>
                     <div id="properties"><p class="muted">Inhalte werden geladen …</p></div>
                 </section>
@@ -90,7 +93,7 @@
     </main>
     <div id="context-menu" class="context-menu" role="menu" aria-label="Elementmenü" hidden></div>
     <noscript><p class="notice error">Zum Bearbeiten muss JavaScript aktiviert sein. Die öffentliche Website funktioniert ohne JavaScript.</p></noscript>
-    <dialog id="publish-dialog" aria-labelledby="publish-title"><h2 id="publish-title">Seite veröffentlichen?</h2><p>Der gespeicherte Entwurf ersetzt den bisher sichtbaren Inhalt dieser Seite.</p><div class="dialog-actions"><button id="cancel-publish" class="secondary">Abbrechen</button><button id="confirm-publish" class="primary">Jetzt veröffentlichen</button></div></dialog>
+    <dialog id="publish-dialog" aria-labelledby="publish-title"><h2 id="publish-title">Seite veröffentlichen?</h2><p>Der gespeicherte Entwurf ersetzt den bisher sichtbaren Inhalt dieser Seite.</p><p id="publish-languages" hidden>Alle Sprachen dieser Seite gehen gemeinsam online – auch die Übersetzungen im gespeicherten Stand.</p><div class="dialog-actions"><button id="cancel-publish" class="secondary">Abbrechen</button><button id="confirm-publish" class="primary">Jetzt veröffentlichen</button></div></dialog>
     <dialog id="preset-dialog" aria-labelledby="preset-title"><h2 id="preset-title">Gestaltung als Vorlage speichern</h2><p>Die Vorlage steht danach für jeden Block auf jeder Seite zur Verfügung.</p><label for="preset-name">Name der Vorlage</label><input id="preset-name" maxlength="60" placeholder="Heller Abschnitt"><p id="preset-error" class="field-error" hidden></p><div class="dialog-actions"><button id="cancel-preset" class="secondary">Abbrechen</button><button id="confirm-preset" class="primary">Vorlage speichern</button></div></dialog>
     <dialog id="reload-dialog" aria-labelledby="reload-title"><h2 id="reload-title">Serverstand laden?</h2><p>Lokale Änderungen und dein Undo-Verlauf werden ersetzt. Sichere deine Änderungen vorher als JSON.</p><div class="dialog-actions"><button id="cancel-reload" class="secondary">Abbrechen</button><button id="confirm-reload" class="primary">Serverstand übernehmen</button></div></dialog>
 </div>