feat(seo): image sitemap, Article schemas on apologetik pro + katechese, edge caching

Sitemap now declares the image:image namespace and emits an entry per recipe
photo (loc, title from recipe name, caption from alt text) — Google Image
Search can discover all recipe images directly instead of relying on crawl.

Pro arg pages get Article JSON-LD (headline, claim as description, layer as
articleSection, voice names as keywords, deduped voice cites as citations)
plus BreadcrumbList. Katechese/zehn-gebote gets inline Article + Breadcrumb
with a Thing reference to "Dekalog" and CreativeWork citation of P. Martin
Ramm FSSP's Glaubenskurs.

Static-content load functions now set Cache-Control:
public,max-age=300,s-maxage=3600,stale-while-revalidate=86400 — applied to
apologetik layout, contra index/arg, pro index/arg, and the new katechese
+page.ts files. Recipe detail uses s-maxage=1800. Picked HTTP caching over
SvelteKit prerender to avoid baking session=null into the navbar of routes
shared with the auth-aware faithLang layout.

src/lib/js/apologetikJsonLd.ts

@@ -1,4 +1,4 @@
-import type { Argument, Archetype } from '$lib/data/apologetik';
+import type { Argument, Archetype, PosArgument, PosVoice } from '$lib/data/apologetik';
 import type { FaithLang } from '$lib/js/faithI18n';
 import { faithSlugFromLang, apologetikSlug } from '$lib/js/faithI18n';
 
@@ -66,3 +66,51 @@ export function generateContraQaJsonLd(
 		},
 	};
 }
+
+export interface ProArgArticleJsonLd {
+	'@context': 'https://schema.org';
+	'@type': 'Article';
+	headline: string;
+	description: string;
+	inLanguage: FaithLang;
+	url: string;
+	mainEntityOfPage: string;
+	author: { '@type': 'Person'; name: string; url: string };
+	publisher: { '@type': 'Person'; name: string; url: string };
+	articleSection: string;
+	keywords?: string;
+	citation?: Array<{ '@type': 'CreativeWork'; name: string }>;
+}
+
+/** Build an Article JSON-LD for a positive (pro) apologetik argument. */
+export function generateProArgArticleJsonLd(
+	arg: PosArgument,
+	voices: Record<string, PosVoice>,
+	lang: FaithLang
+): ProArgArticleJsonLd {
+	const faithSeg = faithSlugFromLang(lang);
+	const apolSeg = apologetikSlug(lang === 'la' ? 'en' : lang);
+	const url = `https://bocken.org/${faithSeg}/${apolSeg}/pro/${arg.id}`;
+
+	const allCites = Object.values(arg.voices).flatMap((v) => v.cites ?? []);
+	const uniqueCites = Array.from(new Set(allCites));
+	const voiceNames = Object.keys(arg.voices)
+		.map((id) => voices[id]?.name ?? id)
+		.join(', ');
+
+	const article: ProArgArticleJsonLd = {
+		'@context': 'https://schema.org',
+		'@type': 'Article',
+		headline: arg.title,
+		description: arg.claim,
+		inLanguage: lang,
+		url,
+		mainEntityOfPage: url,
+		author: { '@type': 'Person', name: 'Alexander Bocken', url: 'https://bocken.org/' },
+		publisher: { '@type': 'Person', name: 'Alexander Bocken', url: 'https://bocken.org/' },
+		articleSection: arg.layer,
+	};
+	if (voiceNames) article.keywords = voiceNames;
+	if (uniqueCites.length) article.citation = uniqueCites.map((name) => ({ '@type': 'CreativeWork', name }));
+	return article;
+}