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>

public/assets/editor-model.js

@@ -1,5 +1,5 @@
-export const labels = { section: 'Sektion', row: 'Zeile', column: 'Spalte', heading: 'Überschrift', text: 'Text', image: 'Bild', button: 'Button', gallery: 'Galerie', postlist: 'Beitragsliste', postnav: 'Beitragsnavigation', iconcard: 'Symbolkarte', stat: 'Kennzahl', quote: 'Kundenstimme', logos: 'Logoleiste', cta: 'Aufruf-Band', contact: 'Kontaktdaten', divider: 'Trennlinie', spacer: 'Abstand', accordion: 'Akkordeon', accordionitem: 'Akkordeon-Eintrag', tabs: 'Tabs', tabitem: 'Tab', form: 'Formular', breadcrumb: 'Brotkrumen', menu: 'Navigation', partialref: 'Verknüpfte Sektion', embed: 'Externer Inhalt', icon: 'Symbol', progress: 'Fortschritt', slider: 'Slider', legal: 'Rechtszeile', social: 'Soziale Profile', html: 'Eigenes HTML' };
-export const icons = { section: '▣', row: '☰', column: '▥', heading: 'H', text: 'T', image: '▧', button: '↗', gallery: '▦', postlist: '☷', postnav: '⇄', iconcard: '◈', stat: '№', quote: '❝', logos: '⬚', cta: '◉', contact: '✆', divider: '—', spacer: '⇳', accordion: '⌵', accordionitem: '·', tabs: '▭', tabitem: '▫', form: '✉', breadcrumb: '⟩', menu: '☰', partialref: '⧉', legal: '§', embed: '⬓', icon: '◆', progress: '▰', slider: '⇄', social: '⚭', html: '</>' };
+export const labels = { section: 'Sektion', row: 'Zeile', column: 'Spalte', heading: 'Überschrift', text: 'Text', image: 'Bild', button: 'Button', gallery: 'Galerie', postlist: 'Beitragsliste', postnav: 'Beitragsnavigation', iconcard: 'Symbolkarte', stat: 'Kennzahl', quote: 'Kundenstimme', logos: 'Logoleiste', cta: 'Aufruf-Band', contact: 'Kontaktdaten', divider: 'Trennlinie', spacer: 'Abstand', accordion: 'Akkordeon', accordionitem: 'Akkordeon-Eintrag', tabs: 'Tabs', tabitem: 'Tab', form: 'Formular', breadcrumb: 'Brotkrumen', menu: 'Navigation', partialref: 'Verknüpfte Sektion', embed: 'Externer Inhalt', icon: 'Symbol', progress: 'Fortschritt', slider: 'Slider', legal: 'Rechtszeile', social: 'Soziale Profile', html: 'Eigenes HTML', language: 'Sprachwahl' };
+export const icons = { section: '▣', row: '☰', column: '▥', heading: 'H', text: 'T', image: '▧', button: '↗', gallery: '▦', postlist: '☷', postnav: '⇄', iconcard: '◈', stat: '№', quote: '❝', logos: '⬚', cta: '◉', contact: '✆', divider: '—', spacer: '⇳', accordion: '⌵', accordionitem: '·', tabs: '▭', tabitem: '▫', form: '✉', breadcrumb: '⟩', menu: '☰', partialref: '⧉', legal: '§', embed: '⬓', icon: '◆', progress: '▰', slider: '⇄', social: '⚭', html: '</>', language: '文' };
 // A namespaced type belongs to a plugin this installation may not have. Such blocks stay in the
 // document, stay selectable and movable, but the editor never edits or fills them.
 /**
@@ -12,7 +12,7 @@ export const CATEGORIES = [
   { name: 'Inhalt', types: ['heading', 'text', 'image', 'button', 'icon', 'divider', 'spacer'] },
   { name: 'Bausteine', types: ['iconcard', 'stat', 'quote', 'cta', 'contact', 'social', 'logos', 'progress'] },
   { name: 'Gruppen', types: ['gallery', 'accordion', 'accordionitem', 'tabs', 'tabitem', 'slider'] },
-  { name: 'Seite und Daten', types: ['postlist', 'postnav', 'breadcrumb', 'menu', 'form', 'legal', 'partialref', 'embed', 'html'] },
+  { name: 'Seite und Daten', types: ['postlist', 'postnav', 'breadcrumb', 'menu', 'language', 'form', 'legal', 'partialref', 'embed', 'html'] },
 ];
 
 /** How many columns a row can be added with. */
@@ -128,6 +128,8 @@ export function createBlock(type) {
   if (type === 'postlist') block.props = { count: 3, category: '', tag: '', layout: 'karten' };
   if (type === 'postnav') block.props = { previousLabel: 'Vorheriger Beitrag', nextLabel: 'Nächster Beitrag' };
   if (type === 'legal') block.props = { label: 'Rechtliches' };
+  // Welche Sprachen es gibt, weiß die Website; der Block sagt nur, ob er Kürzel oder Namen zeigt.
+  if (type === 'language') block.props = { display: 'code' };
   // Leer eingefuegt: nichts steht auf der Seite, bis jemand Code eintraegt.
   if (type === 'html') block.props = { html: '' };
   if (type === 'iconcard') block.props = { icon: 'check', title: 'Deine Leistung', text: 'Beschreibe hier kurz, worum es geht.', href: '' };
@@ -180,6 +182,7 @@ export function repairSchema(document) {
     }
   };
   walk(document.blocks);
+  if (document.translations) upgradeDocument(document, 27);
   return document;
 }
 
@@ -194,6 +197,7 @@ export function upgradeForType(document, type) {
   if (type === 'postnav') upgradeDocument(document, 18);
   if (type === 'legal') upgradeDocument(document, 19);
   if (type === 'html') upgradeDocument(document, 24);
+  if (type === 'language') upgradeDocument(document, 27);
   if (['iconcard', 'stat', 'quote', 'logos', 'cta', 'contact', 'divider', 'spacer', 'accordion', 'accordionitem'].includes(type)) upgradeDocument(document, 6);
   if (type === 'tabs' || type === 'tabitem') upgradeDocument(document, 7);
   if (type === 'form') upgradeDocument(document, 8);
@@ -344,7 +348,7 @@ export const devices = { desktop: 'Desktop', tablet: 'Tablet', mobile: 'Mobil' }
 // blieb bei 12 stehen, während Bausteine schon v13 bis v15 verlangten: in einem aktuellen Dokument
 // liess sich dann gar nichts mehr einfügen, und ein Symbol, ein Slider oder ein externer Inhalt
 // nirgends. Eine Zahl, an einer Stelle.
-export const SCHEMA_VERSION = 26;
+export const SCHEMA_VERSION = 27;
 
 export const VISIBILITY = { all: 'Auf allen Geräten', desktop: 'Nur Desktop', tablet: 'Nur Tablet', mobile: 'Nur Mobil', 'hide-desktop': 'Auf Desktop ausblenden', 'hide-tablet': 'Auf Tablet ausblenden', 'hide-mobile': 'Auf Mobil ausblenden', hidden: 'Überall ausblenden' };