Add an own-HTML block, and build the DEEG offers page on the embed block

Umut asked for a block that takes custom HTML, and for an iframe on a new
DEEG offers page. Only one of those was missing.

New core block "Eigenes HTML" (document schema v24): one property, the
markup, up to 20.000 characters, written to the page unchanged. Changing it
is reserved for administrators and compared against what is stored - on
saving, on saving an area, and on restoring an older revision - exactly like
an own script. <script> and <iframe> are refused with the way to the right
place instead of being swallowed by the content security policy: scripts
belong in the script field, frames in the "Externer Inhalt" block, because
only that one asks for consent and puts the host into frame-src (ADR 106).

DEEG: /angebote existed as a draft with placeholder text. It is now built
like the legal pages - small caps line, large light heading, lead on the
tinted band - with the IS24 result list below it and a line pointing to the
portal and to the contact form. Navigation and the offers band on the home
page point there. The consent question is switched on, so the frame loads
only after the visitor agrees, and both the banner and the placeholder carry
the site's own shapes and colours.

Co-Authored-By: Claude Opus 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' };
-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: '⚭' };
+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: '</>' };
 // 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'] },
+  { name: 'Seite und Daten', types: ['postlist', 'postnav', 'breadcrumb', 'menu', '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' };
+  // 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: '' };
   if (type === 'stat') block.props = { value: '15+', label: 'Jahre Erfahrung' };
   if (type === 'quote') block.props = { text: 'Ein Satz, den eine Kundin oder ein Kunde über dich gesagt hat.', author: 'Name', role: '', rating: 5 };
@@ -160,6 +162,7 @@ export function upgradeForType(document, type) {
   if (type === 'postlist') upgradeDocument(document, 18);
   if (type === 'postnav') upgradeDocument(document, 18);
   if (type === 'legal') upgradeDocument(document, 19);
+  if (type === 'html') upgradeDocument(document, 24);
   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);
@@ -310,7 +313,7 @@ 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 = 23;
+export const SCHEMA_VERSION = 24;
 
 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' };