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>

src/Content/SiteSettings.php

@@ -89,6 +89,13 @@ final class SiteSettings
         'consentAccentInk' => '',
         'privacyPath' => '',
         'imprintPath' => '',
+        // Die weiteren Sprachen neben der Hauptsprache (ADR 111), gepflegt über Languages::save.
+        // Leer heißt: einsprachig - und dann ist nirgends etwas von Übersetzungen zu sehen.
+        'languages' => [],
+        // Namen von Kategorien und Schlagwörtern je weiterer Sprache: {en: {"category:projekte": "Projects"}}.
+        'termNames' => [],
+        // Überschrift und Text des Einwilligungshinweises je weiterer Sprache: {en: {title, text}}.
+        'consentTexts' => [],
     ];
 
     /** Die Wochentage, wie schema.org sie nennt, mit deutscher Beschriftung für das Formular. */
@@ -191,6 +198,10 @@ final class SiteSettings
         $values = self::DEFAULTS;
         // Assigned separately, so saving company data cannot clear the error page.
         $values['notFoundPageId'] = $this->load()['notFoundPageId'];
+        // Ebenso die Sprachen: sie haben einen eigenen Bildschirm mit eigener Prüfung.
+        $values['languages'] = $this->load()['languages'];
+        $values['termNames'] = $this->load()['termNames'];
+        $values['consentTexts'] = $this->load()['consentTexts'];
         foreach (['legalName' => 200, 'description' => 300, 'phone' => 40, 'email' => 120, 'street' => 120, 'postalCode' => 16, 'city' => 120] as $key => $max) {
             $values[$key] = mb_substr(trim((string) ($input[$key] ?? '')), 0, $max);
         }
@@ -403,6 +414,71 @@ final class SiteSettings
         $this->loaded = null;
     }
 
+    /**
+     * Nur die Sprachen ändern, alles andere unberührt lassen. Geprüft wird in Languages::save.
+     *
+     * @param list<string> $codes
+     */
+    public function saveLanguages(array $codes): void
+    {
+        $this->db->transactional(function () use ($codes): void {
+            $raw = $this->db->fetchOne('SELECT settings FROM website WHERE id = ?', ['default']);
+            $stored = is_string($raw) ? json_decode($raw, true, 512, JSON_THROW_ON_ERROR) : [];
+            $stored = is_array($stored) ? $stored : [];
+            $stored['languages'] = array_values($codes);
+            $this->db->executeStatement('UPDATE website SET settings = ? WHERE id = ?', [
+                json_encode($stored, JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE), 'default',
+            ]);
+        });
+        $this->loaded = null;
+    }
+
+    /**
+     * Die Texte der Einstellungen in weiteren Sprachen (ADR 111): Namen von Kategorien und
+     * Schlagwörtern sowie Überschrift und Text des Einwilligungshinweises. Alles andere bleibt.
+     *
+     * @param array<string, array<string, string>> $names   Sprache => "art:adresse" => Name
+     * @param array<string, array<string, string>> $consent Sprache => {title, text}
+     */
+    public function saveLanguageTexts(array $names, array $consent = []): void
+    {
+        $consentClean = [];
+        foreach ($consent as $locale => $texts) {
+            if (!is_string($locale) || !isset(Languages::CATALOG[$locale]) || !is_array($texts)) {
+                continue;
+            }
+            foreach (['title' => 80, 'text' => 600] as $key => $max) {
+                $text = mb_substr(trim((string) ($texts[$key] ?? '')), 0, $max);
+                if ('' !== $text) {
+                    $consentClean[$locale][$key] = $text;
+                }
+            }
+        }
+        $clean = [];
+        foreach ($names as $locale => $entries) {
+            if (!is_string($locale) || !isset(Languages::CATALOG[$locale]) || !is_array($entries)) {
+                continue;
+            }
+            foreach ($entries as $key => $name) {
+                $name = mb_substr(trim((string) $name), 0, 120);
+                if ('' !== $name && 1 === preg_match('/^(category|tag):[a-z0-9-]{1,80}$/D', (string) $key)) {
+                    $clean[$locale][(string) $key] = $name;
+                }
+            }
+        }
+        $this->db->transactional(function () use ($clean, $consentClean): void {
+            $raw = $this->db->fetchOne('SELECT settings FROM website WHERE id = ?', ['default']);
+            $stored = is_string($raw) ? json_decode($raw, true, 512, JSON_THROW_ON_ERROR) : [];
+            $stored = is_array($stored) ? $stored : [];
+            $stored['termNames'] = $clean;
+            $stored['consentTexts'] = $consentClean;
+            $this->db->executeStatement('UPDATE website SET settings = ? WHERE id = ?', [
+                json_encode($stored, JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE), 'default',
+            ]);
+        });
+        $this->loaded = null;
+    }
+
     /**
      * Which of the two mandatory pages are missing, by their settings key.
      *