@grackle-ai/server has Missing Content-Security-Policy and X-Frame-Options Headers

Summary

### Impact

The HTTP server does not set `Content-Security-Policy`, `X-Frame-Options`, or `X-Content-Type-Options` headers on any response. This reduces defense-in-depth against XSS, clickjacking, and MIME-sniffing attacks.

While the current XSS attack surface is small (React-markdown is configured safely, no `dangerouslySetInnerHTML`, Vite does not generate source maps), the absence of these headers means any future XSS vulnerability would have no secondary defense layer.

**Affected code:** - `packages/server/src/index.ts` — all `res.writeHead()` calls only set `Content-Type`, with no security headers

### Patches

0.70.4

**Fix:** Add security headers to all HTML/API responses: ```typescript res.writeHead(200, { "Content-Type": contentType, "Content-Security-Policy": "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:", "X-Frame-Options": "DENY", "X-Content-Type-Options": "nosniff" }); ```

### Workarounds

Use a reverse proxy (nginx, Caddy) in front of the Grackle server to inject security headers.

### References

- CWE-693: Protection Mechanism Failure - OWASP: HTTP Security Response Headers - File: `packages/server/src/index.ts`