Initial MVP: DocFast PDF API

- HTML/Markdown to PDF conversion via Puppeteer
- Invoice and receipt templates
- API key auth + rate limiting
- Dockerfile for deployment

src/middleware/auth.ts

@@ -0,0 +1,23 @@
+import { Request, Response, NextFunction } from "express";
+
+const API_KEYS = new Set(
+  (process.env.API_KEYS || "test-key-123").split(",").map((k) => k.trim())
+);
+
+export function authMiddleware(
+  req: Request,
+  res: Response,
+  next: NextFunction
+): void {
+  const header = req.headers.authorization;
+  if (!header?.startsWith("Bearer ")) {
+    res.status(401).json({ error: "Missing API key. Use: Authorization: Bearer <key>" });
+    return;
+  }
+  const key = header.slice(7);
+  if (!API_KEYS.has(key)) {
+    res.status(403).json({ error: "Invalid API key" });
+    return;
+  }
+  next();
+}