Episode 12/13: CrowdSec next to fail2ban, and an AppSec WAF in Caddy

Measured on the demo box against the same 24h of real traffic.

Episode 12 (detection, blocklist, firewall):
- crowdsec/ with install notes and the traps: port 8080 clash, empty first
  blocklist pull, replay forensic-mode dropping events (FIFO workaround),
  ssh-time-based-bf shipping remediation:false, the AppSec collections that
  refuse to start without extra rules.
- firewall bouncer in nftables mode (input + forward), which blocks
  Docker-published ports and survives ufw reload; iptables/DOCKER-USER does not.
- HARDENING.md episode 12 section with the numbers: fail2ban 4 banned IPs vs
  CrowdSec 23 detected / 1 blocked, blocklist overlap 50% of IPs but 19% of
  attempts, and the mode=normal blind spot for key-only root attempts.

Episode 13 (AppSec WAF):
- caddy/Dockerfile now builds the CrowdSec bouncer and AppSec handler alongside
  rate-limit, pinned to v0.14.1.
- Caddyfile imports a crowdsec snippet (bouncer + appsec) on every site except
  vpn; compose passes CROWDSEC_BOUNCER_KEY and host.docker.internal.
- Measured: virtual patching blocks known CVEs only (7 of 41 probes, near-zero
  false positives); OWASP CRS raises that to 27 of 41 but breaks git push and
  wiki editing at default paranoia. Default stays vpatch+generic.

fail2ban config unchanged. No secrets or real domains/IPs in tracked files.

crowdsec/firewall-bouncer.yaml

@@ -0,0 +1,12 @@
+# episode 12: the keys changed in /etc/crowdsec/bouncers/crowdsec-firewall-bouncer.yaml
+# (the package writes the rest, including api_url and api_key).
+#
+# nftables mode instead of the iptables default. The bouncer then owns its
+# own tables (ip crowdsec, ip6 crowdsec6) with hooks on input AND forward at
+# priority -10, so it drops before Docker's FORWARD rules, and `ufw reload`
+# does not touch it. In iptables mode you must add DOCKER-USER to
+# iptables_chains, and every `ufw reload` silently removes the rule again.
+mode: nftables
+nftables_hooks:
+  - input
+  - forward