feat(nixnuc): rate-limit ytdlfin /health endpoint in nginx

[genebean]

Summary

• Adds limit_req_zone $binary_remote_addr zone=ytdlfin_health:1m rate=6r/m; to appendHttpConfig so the zone is declared in the http {} block
• Adds location = /health to the ytdlfin virtual host with limit_req zone=ytdlfin_health burst=3 nodelay; — allows short bursts while capping sustained unauthenticated traffic at 6 requests/min per IP
• Companion to the ytdlfin feat/health-endpoint PR which adds the actual /health endpoint

Test plan

• nixos-rebuild applies cleanly on nixnuc
• curl https://ytdlfin.<domain>/health returns 200 {"status":"ok"}
• Rapid repeated curls beyond the burst limit receive 503 from nginx
• Uptime Kuma monitor on /health stays green at its normal poll interval

🤖 Generated with Claude Code

[genebean]

Validated via

$ URL="https://ytdlfin.home.technicalissues.us/health"
$ for i in {1..20}; do
  code=$(curl -s -o /dev/null -w "%{http_code}" "$URL")
  echo "Request $i: HTTP $code"
  [ "$code" = "503" ] && { echo "Got 503 — stopping."; break; }
done
Request 1: HTTP 200
Request 2: HTTP 200
Request 3: HTTP 200
Request 4: HTTP 200
Request 5: HTTP 503
Got 503 — stopping.