v0.4.0: Remove free tier, add public demo endpoint with watermark

- Remove free account signup flow entirely
- Add POST /v1/demo/html and /v1/demo/markdown (public, no auth)
- Demo: 5 requests/hour per IP, 50KB body limit, watermarked PDFs
- Landing page: interactive playground replaces 'Get Free API Key'
- Pricing: Demo (free) + Pro (€9/mo), no more Free tier
- /v1/signup returns 410 Gone with redirect to demo/pro
- Keep /v1/recover for existing Pro users
- Update JSON-LD, API discovery, verify page text

src/routes/demo.ts

@@ -0,0 +1,146 @@
+import { Router, Request, Response } from "express";
+import rateLimit from "express-rate-limit";
+import { renderPdf } from "../services/browser.js";
+import { markdownToHtml, wrapHtml } from "../services/markdown.js";
+import logger from "../services/logger.js";
+
+const router = Router();
+
+const WATERMARK_HTML = `<div style="position:fixed;bottom:0;left:0;right:0;background:rgba(52,211,153,0.92);color:#0b0d11;text-align:center;padding:8px;font-family:sans-serif;font-size:12px;font-weight:bold;z-index:999999;letter-spacing:0.3px;">Generated by DocFast — docfast.dev | Upgrade to Pro for clean PDFs</div>`;
+
+function injectWatermark(html: string): string {
+  if (html.includes("</body>")) {
+    return html.replace("</body>", WATERMARK_HTML + "</body>");
+  }
+  return html + WATERMARK_HTML;
+}
+
+// 5 requests per hour per IP
+const demoLimiter = rateLimit({
+  windowMs: 60 * 60 * 1000,
+  max: 5,
+  message: { error: "Demo limit reached (5/hour). Get a Pro API key at https://docfast.dev for unlimited access." },
+  standardHeaders: true,
+  legacyHeaders: false,
+  keyGenerator: (req) => req.ip || req.socket.remoteAddress || "unknown",
+});
+
+router.use(demoLimiter);
+
+interface DemoBody {
+  html?: string;
+  markdown?: string;
+  css?: string;
+  format?: string;
+  landscape?: boolean;
+  margin?: { top?: string; right?: string; bottom?: string; left?: string };
+  printBackground?: boolean;
+  filename?: string;
+}
+
+function sanitizeFilename(name: string): string {
+  return name.replace(/[\x00-\x1f"\\\r\n]/g, "").trim() || "document.pdf";
+}
+
+// POST /v1/demo/html
+router.post("/html", async (req: Request & { acquirePdfSlot?: () => Promise<void>; releasePdfSlot?: () => void }, res: Response) => {
+  let slotAcquired = false;
+  try {
+    const ct = req.headers["content-type"] || "";
+    if (!ct.includes("application/json")) {
+      res.status(415).json({ error: "Unsupported Content-Type. Use application/json." });
+      return;
+    }
+
+    const body: DemoBody = typeof req.body === "string" ? { html: req.body } : req.body;
+    if (!body.html) {
+      res.status(400).json({ error: "Missing 'html' field" });
+      return;
+    }
+
+    if (req.acquirePdfSlot) {
+      await req.acquirePdfSlot();
+      slotAcquired = true;
+    }
+
+    const fullHtml = body.html.includes("<html")
+      ? injectWatermark(body.html)
+      : injectWatermark(wrapHtml(body.html, body.css));
+
+    const pdf = await renderPdf(fullHtml, {
+      format: body.format || "A4",
+      landscape: body.landscape || false,
+      printBackground: body.printBackground !== false,
+      margin: body.margin || { top: "0", right: "0", bottom: "0", left: "0" },
+    });
+
+    const filename = sanitizeFilename(body.filename || "demo.pdf");
+    res.setHeader("Content-Type", "application/pdf");
+    res.setHeader("Content-Disposition", `attachment; filename="${filename}"`);
+    res.setHeader("Content-Length", pdf.length);
+    res.send(pdf);
+  } catch (err: any) {
+    if (err.message === "QUEUE_FULL") {
+      res.status(503).json({ error: "Server busy. Please try again in a moment." });
+    } else if (err.message === "PDF_TIMEOUT") {
+      res.status(504).json({ error: "PDF generation timed out." });
+    } else {
+      logger.error({ err }, "Demo HTML conversion failed");
+      res.status(500).json({ error: "PDF generation failed." });
+    }
+  } finally {
+    if (slotAcquired && req.releasePdfSlot) req.releasePdfSlot();
+  }
+});
+
+// POST /v1/demo/markdown
+router.post("/markdown", async (req: Request & { acquirePdfSlot?: () => Promise<void>; releasePdfSlot?: () => void }, res: Response) => {
+  let slotAcquired = false;
+  try {
+    const ct = req.headers["content-type"] || "";
+    if (!ct.includes("application/json")) {
+      res.status(415).json({ error: "Unsupported Content-Type. Use application/json." });
+      return;
+    }
+
+    const body: DemoBody = typeof req.body === "string" ? { markdown: req.body } : req.body;
+    if (!body.markdown) {
+      res.status(400).json({ error: "Missing 'markdown' field" });
+      return;
+    }
+
+    if (req.acquirePdfSlot) {
+      await req.acquirePdfSlot();
+      slotAcquired = true;
+    }
+
+    const htmlContent = markdownToHtml(body.markdown);
+    const fullHtml = injectWatermark(wrapHtml(htmlContent, body.css));
+
+    const pdf = await renderPdf(fullHtml, {
+      format: body.format || "A4",
+      landscape: body.landscape || false,
+      printBackground: body.printBackground !== false,
+      margin: body.margin || { top: "0", right: "0", bottom: "0", left: "0" },
+    });
+
+    const filename = sanitizeFilename(body.filename || "demo.pdf");
+    res.setHeader("Content-Type", "application/pdf");
+    res.setHeader("Content-Disposition", `attachment; filename="${filename}"`);
+    res.setHeader("Content-Length", pdf.length);
+    res.send(pdf);
+  } catch (err: any) {
+    if (err.message === "QUEUE_FULL") {
+      res.status(503).json({ error: "Server busy. Please try again in a moment." });
+    } else if (err.message === "PDF_TIMEOUT") {
+      res.status(504).json({ error: "PDF generation timed out." });
+    } else {
+      logger.error({ err }, "Demo markdown conversion failed");
+      res.status(500).json({ error: "PDF generation failed." });
+    }
+  } finally {
+    if (slotAcquired && req.releasePdfSlot) req.releasePdfSlot();
+  }
+});
+
+export { router as demoRouter };