feat(security+obs): SSRF allowlist, HTML sanitization, timing-safe tokens, fetch timeouts, structured logger

Security:
  - cms-images / cms-files now share resolveCmsSource (cms-source.server.ts)
    which enforces an allowlist: asset filename, absolute path on the CMS
    host, or full URL exact-matching the configured CMS host+protocol.
    Foreign hosts, protocol-relative URLs and path traversal return 400.
  - markdown-safe.ts is the single configured marked entrypoint; it
    disables raw HTML rendering globally (renderer.html() returns ''),
    removing the inline script/iframe injection vector via markdown.
    All 8 marked imports across components and loaders now go through it.
  - sanitize-blocks.server.ts walks resolved page/post content and runs
    HtmlBlock html fields through sanitize-html with a tight allowlist
    (no script/style/on*, only youtube/vimeo/spotify iframes, mailto/tel
    plus http(s) schemes, target=_blank gets rel=noopener).
  - Webhook tokens (revalidate, cache/clear) compared via
    crypto.timingSafeEqual through auth-token.server.ts.
  - cms.ts wraps every fetch in cmsFetch(): 5 s default timeout via
    AbortSignal.timeout, override per call or globally via
    PUBLIC_CMS_FETCH_TIMEOUT_MS. Stops slow CMS responses from pinning
    SSR workers indefinitely.

Observability:
  - log.server.ts gives logWarn / logError / logInfo with scope + context;
    swallowed catch {} blocks in hooks, layout.server, +page.server,
    [...slug]/+page.server and sitemap now log instead of going silent.

Routing:
  - Legacy /blog, /blog/page/:n, /blog/tag/:t and /p/:slug stub routes
    deleted; their 301 redirects moved into hooks.server.ts so the
    request never enters the SvelteKit page pipeline.

Tests (vitest, server-side):
  - auth-token.server.test.ts (6 cases for constant-time compare)
  - cms-source.server.test.ts  (8 cases for SSRF allowlist)
  - sanitize-blocks.server.test.ts (9 cases for sanitizer + walker)
  All 23 green.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/lib/markdown-safe.ts

@@ -0,0 +1,37 @@
+/**
+ * Zentral konfigurierter `marked`-Parser. Wichtig: deaktiviert das
+ * Rendern von **rohem HTML** in Markdown-Quellen — sonst kann ein
+ * Editor (oder ein kompromittiertes Editor-Konto) `<script>` oder
+ * `<iframe>`-Tags direkt einschleusen. Marked rendert sie standardmäßig
+ * wörtlich durch.
+ *
+ * `marked` ist Singleton: einmaliger Side-Effect-Import setzt die
+ * Renderer-Hooks global. Komponenten und Loader importieren `marked`
+ * von hier statt direkt von "marked".
+ *
+ * Komponenten, die `marked.parse(...)` aufrufen, sollten das Resultat
+ * weiterhin nur über `{@html}` einsetzen — der Sanitizer hier deckt das
+ * Markdown-→-HTML-Mapping ab. Roh-HTML-Felder (HtmlBlock) werden zusätzlich
+ * über `$lib/sanitize-blocks.server` gefiltert.
+ */
+import { marked } from 'marked';
+
+let configured = false;
+
+function configure() {
+  if (configured) return;
+  marked.setOptions({ gfm: true });
+  marked.use({
+    renderer: {
+      // Inline raw HTML: `<...>` → bleibt wörtlich als Text stehen.
+      html() {
+        return '';
+      },
+    },
+  });
+  configured = true;
+}
+
+configure();
+
+export { marked };