Session 45: support email, audit fixes (template validation, content-type, admin auth, waitUntil)

- Added support@docfast.dev to footer, impressum, terms, landing page, openapi.json
- Fixed audit #6: Template render validates required fields (400 on missing)
- Fixed audit #7: Content-Type check on markdown/URL routes (415)
- Fixed audit #11: /v1/usage and /v1/concurrency now require ADMIN_API_KEY
- Fixed audit Critical #3: URL convert uses domcontentloaded instead of networkidle0

public/terms.html

@@ -93,7 +93,7 @@ footer .container { display: flex; justify-content: space-between; align-items:
       <li><strong>Price:</strong> €9 per month</li>
       <li><strong>Monthly limit:</strong> 10,000 PDF conversions</li>
       <li><strong>Rate limit:</strong> Higher limits based on fair use</li>
-      <li><strong>Support:</strong> Priority email support</li>
+      <li><strong>Support:</strong> Priority email support (<a href="mailto:support@docfast.dev">support@docfast.dev</a>)</li>
       <li><strong>Billing:</strong> Monthly subscription via Stripe</li>
     </ul>
 
@@ -252,6 +252,7 @@ footer .container { display: flex; justify-content: space-between; align-items:
       <a href="/docs">Docs</a>
       <a href="/health">API Status</a>
       <a href="/#change-email" class="open-email-change">Change Email</a>
+      <a href="mailto:support@docfast.dev">Support</a>
       <a href="/impressum">Impressum</a>
       <a href="/privacy">Privacy Policy</a>
       <a href="/terms">Terms of Service</a>