Episode 10: hardening - firewall rules Docker cannot bypass, Caddy access log and rate limiting, fail2ban in the right chain

- hardening/: ufw after.rules block for DOCKER-USER (ctorigdstport, not dport),
  fail2ban jail.local with sshd (systemd backend) and caddy-probes (chain DOCKER-USER),
  filter for the JSON access log, sshd hardening.conf, README with the order and
  the two traps measured in the episode
- caddy/Dockerfile: xcaddy build with caddy-ratelimit, compose builds the image
- Caddyfile: common snippet (JSON access log, Server header stripped), vault /admin 404,
  rate_limit zones on the vault token endpoint and the git login form
- HARDENING.md: firewall and fail2ban sections rewritten around what the port scan saw

Claude-Session: https://claude.ai/code/session_017iP581CYtPfxdZYPPAyWZA

hardening/fail2ban/filter.d/caddy-probes.conf

@@ -0,0 +1,8 @@
+# /etc/fail2ban/filter.d/caddy-probes.conf   (episode 10)
+# Matches the JSON access log: bots that harvest 401/403/404/429 (probing for
+# /.env, /wp-login.php, /xmlrpc.php, or hammering a login past the rate limit).
+# The whole log entry is one line; client_ip sits in the request object and
+# status at the top level, so client_ip always comes before status.
+[Definition]
+failregex = ^.*"client_ip":"<HOST>".*"status":(401|403|404|429)\b.*$
+ignoreregex =