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/sanitize-blocks.server.test.ts

@@ -0,0 +1,70 @@
+import { describe, expect, it } from 'vitest';
+import { sanitizeBlocks, sanitizeUntrustedHtml } from './sanitize-blocks.server';
+
+describe('sanitizeUntrustedHtml', () => {
+  it('strips <script>', () => {
+    const out = sanitizeUntrustedHtml('<p>ok</p><script>alert(1)</script>');
+    expect(out).not.toContain('script');
+    expect(out).toContain('ok');
+  });
+
+  it('strips on* event handlers', () => {
+    const out = sanitizeUntrustedHtml('<a href="#" onclick="alert(1)">x</a>');
+    expect(out).not.toContain('onclick');
+  });
+
+  it('strips javascript: URLs', () => {
+    const out = sanitizeUntrustedHtml('<a href="javascript:alert(1)">x</a>');
+    expect(out).not.toContain('javascript');
+  });
+
+  it('keeps allowed tags + attributes', () => {
+    const out = sanitizeUntrustedHtml('<p class="foo"><strong>bold</strong></p>');
+    expect(out).toContain('<p class="foo">');
+    expect(out).toContain('<strong>bold</strong>');
+  });
+
+  it('allows iframes only from approved hosts', () => {
+    const ok = sanitizeUntrustedHtml('<iframe src="https://www.youtube.com/embed/x"></iframe>');
+    expect(ok).toContain('youtube.com');
+    const bad = sanitizeUntrustedHtml('<iframe src="https://evil.com/x"></iframe>');
+    expect(bad).not.toContain('evil');
+  });
+
+  it('adds rel=noopener on target=_blank', () => {
+    const out = sanitizeUntrustedHtml('<a href="https://x.com" target="_blank">x</a>');
+    expect(out).toContain('rel="noopener noreferrer"');
+  });
+});
+
+describe('sanitizeBlocks (walker)', () => {
+  it('mutates html-block fields in place', () => {
+    const tree = {
+      row1Content: [
+        { _type: 'html', html: '<p>safe</p><script>x</script>' },
+        { _type: 'markdown', content: 'untouched' },
+      ],
+    };
+    sanitizeBlocks(tree);
+    expect(tree.row1Content[0].html).not.toContain('script');
+    expect(tree.row1Content[0].html).toContain('safe');
+    expect((tree.row1Content[1] as { content: string }).content).toBe('untouched');
+  });
+
+  it('walks nested arrays', () => {
+    const tree = {
+      sections: [
+        { items: [{ _type: 'html', html: '<img src=x onerror=alert(1)>' }] },
+      ],
+    };
+    sanitizeBlocks(tree);
+    const html = (tree.sections[0].items[0] as { html: string }).html;
+    expect(html).not.toContain('onerror');
+  });
+
+  it('handles non-object inputs gracefully', () => {
+    expect(() => sanitizeBlocks(null)).not.toThrow();
+    expect(() => sanitizeBlocks('string')).not.toThrow();
+    expect(() => sanitizeBlocks([1, 2, 3])).not.toThrow();
+  });
+});