Add HAProxy PoW challenge, simple bad bot blocking, and adjust mounts

Replace single deploy/haproxy.cfg with deploy/haproxy/{haproxy.cfg,challenge.html}.
HAProxy now runs a WebCrypto-based proof-of-work challenge using a stick-table,
URI normalization and a challenge backend. docker-compose mounts the haproxy
directory, and also switches the site DB volume to ./db to be consistent. Update robots.txt.ts to
add a honeypot path for bad bot blocking.

src/pages/robots.txt.ts

@@ -69,6 +69,9 @@ DisallowAITraining: /
 Content-Usage: ai=n
 Allow: /
 
+User-Agent: *
+Disallow: /blokmeplz/
+
 Sitemap: ${sitemapURL.href}
 `;