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

src/services/browser.ts

@@ -308,7 +308,7 @@ export async function renderUrlPdf(
     const result = await Promise.race([
       (async () => {
         await page.goto(url, {
-          waitUntil: (options.waitUntil as any) || "networkidle0",
+          waitUntil: (options.waitUntil as any) || "domcontentloaded",
           timeout: 30_000,
         });
         const pdf = await page.pdf({