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/cms-source.server.test.ts

@@ -0,0 +1,63 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+const ORIG_ENV = { ...process.env };
+
+beforeEach(() => {
+  vi.resetModules();
+  process.env.PUBLIC_CMS_URL = 'https://cms.example.com';
+});
+
+afterEach(() => {
+  process.env = { ...ORIG_ENV };
+});
+
+async function loadResolver() {
+  const mod = await import('./cms-source.server');
+  return mod.resolveCmsSource;
+}
+
+describe('resolveCmsSource', () => {
+  it('accepts asset filename', async () => {
+    const resolve = await loadResolver();
+    expect(resolve('photo.jpg')).toBe('https://cms.example.com/api/assets/photo.jpg');
+  });
+
+  it('accepts absolute path on CMS host', async () => {
+    const resolve = await loadResolver();
+    expect(resolve('/api/assets/foo.png')).toBe('https://cms.example.com/api/assets/foo.png');
+  });
+
+  it('accepts full URL on CMS host', async () => {
+    const resolve = await loadResolver();
+    expect(resolve('https://cms.example.com/some/path')).toBe('https://cms.example.com/some/path');
+  });
+
+  it('rejects foreign host', async () => {
+    const resolve = await loadResolver();
+    expect(resolve('https://attacker.com/exploit.jpg')).toBeNull();
+  });
+
+  it('rejects http when CMS uses https', async () => {
+    const resolve = await loadResolver();
+    expect(resolve('http://cms.example.com/foo')).toBeNull();
+  });
+
+  it('rejects protocol-relative URLs', async () => {
+    const resolve = await loadResolver();
+    expect(resolve('//attacker.com/x.jpg')).toBeNull();
+  });
+
+  it('rejects path traversal in filename', async () => {
+    const resolve = await loadResolver();
+    expect(resolve('../etc/passwd')).toBeNull();
+    expect(resolve('./hidden')).toBeNull();
+  });
+
+  it('encodes "javascript:" payloads as harmless asset filename', async () => {
+    const resolve = await loadResolver();
+    // Kein Schema-Marker (kein "://") → wird als Filename behandelt und
+    // url-encoded an /api/assets angehängt. Server liefert 404 zurück,
+    // keine Code-Ausführung möglich.
+    expect(resolve('javascript:alert(1)')).toContain('/api/assets/javascript%3Aalert');
+  });
+});