Add no-keycloak and CrowdSec script variants; restore originals

Provide three tiers of the install script for both 24.04 and 26.04:

- Originals (ubuntu-post-install-24.04.sh / -26.04.sh): restored to their
  true original state, with Keycloak intact, as a fallback baseline. (This
  reverts the in-place Keycloak removal from the previous commit; the cleanup
  now lives in the -no-keycloak variants instead.)
- -no-keycloak.sh: Keycloak fully removed, Authelia as the SSO/2FA option.
- -crowdsec.sh: builds on -no-keycloak and replaces fail2ban entirely with
  CrowdSec (SSH via auth.log/sshd collection, Caddy via caddy collection + log
  acquisition, firewall bouncer for enforcement, plus geo-blocking and
  community IP-reputation blocklists).

Add SCRIPT-VARIANTS.md documenting the three tiers and how the Authelia /
fail2ban / CrowdSec security layers differ.

All variants pass 'bash -n'.

https://claude.ai/code/session_017eA2qqq9jfF2tNtpUYL8vK

SCRIPT-VARIANTS.md

@@ -0,0 +1,48 @@
+# Install Script Variants
+
+This repo ships the post-install script in three tiers, for both Ubuntu 24.04
+and 26.04. Pick **one** and run it — they are mutually exclusive (each is a
+complete, standalone script).
+
+| File | Keycloak | SSO | Intrusion prevention |
+|------|----------|-----|----------------------|
+| `ubuntu-post-install-<ver>.sh` | ✅ included | Keycloak **or** Authelia | fail2ban (SSH + Caddy) |
+| `ubuntu-post-install-<ver>-no-keycloak.sh` | ❌ removed | Authelia | fail2ban (SSH + Caddy) |
+| `ubuntu-post-install-<ver>-crowdsec.sh` | ❌ removed | Authelia | **CrowdSec** (replaces fail2ban) |
+
+`<ver>` is `24.04` or `26.04`.
+
+## Which one?
+
+- **Original (`.sh`)** — unchanged baseline, kept for fallback. Still offers
+  Keycloak in the menu.
+- **`-no-keycloak`** — same as original but with Keycloak fully removed.
+  Authelia is the SSO + 2FA option. Use this if you never got Keycloak running
+  and have standardized on Authelia.
+- **`-crowdsec`** — builds on `-no-keycloak` and swaps fail2ban out for
+  [CrowdSec](https://www.crowdsec.net/):
+  - SSH brute-force protection (CrowdSec reads `/var/log/auth.log` via the
+    `crowdsecurity/sshd` collection)
+  - Caddy HTTP auth abuse (the `crowdsecurity/caddy` collection + a log
+    acquisition at `/etc/crowdsec/acquis.d/caddy.yaml`)
+  - Enforcement via `crowdsec-firewall-bouncer-iptables`
+  - **Geo-blocking + community IP-reputation blocklists** — the capability
+    that fail2ban and Authelia both lack
+
+## Notes on the security layers
+
+- **Authelia** handles per-account failed-login *regulation* (lockout). It does
+  **not** do geo-blocking.
+- **fail2ban** bans IPs at the firewall based on Caddy log patterns
+  (401/403/429). No geo-blocking, not credential-aware.
+- **CrowdSec** covers SSH + Caddy from a single agent, adds geo/ASN enrichment
+  and crowd-sourced reputation, and is the modern successor to fail2ban.
+
+Useful CrowdSec commands after install:
+
+```bash
+sudo cscli metrics              # overview / parsing health
+sudo cscli decisions list       # current bans
+sudo cscli alerts list          # detections
+sudo cscli decisions delete --ip <IP>   # unban
+```