Add security-dashboard: Asterisk failed-connections + CrowdSec bans, one page

New service, native on the host (not Docker) so it can call cscli and
read Asterisk's security log directly without bridging the
container/host boundary or exposing CrowdSec LAPI credentials to a
containerized frontend.

- Security Log tab: parses ~/docker/asterisk-digital-ocean/logs/full
  for SIP auth failures (wrong password, unknown extension, etc.) with
  timestamp/account/remote IP, classified by severity.
- CrowdSec tab: current bans via cscli, a delete/unban button per
  entry, and ASN-exempt management for the Asterisk brute-force
  scenarios (services/crowdsec.sh) without SSHing in.
- Link out to the existing Asterisk web admin (reads its domain from
  asterisk-digital-ocean's own .env, doesn't hardcode or embed it).

Runs as a dedicated unprivileged system user (secdash), with sudo
scoped to exactly three commands via /etc/sudoers.d/security-dashboard
(cscli decisions delete --id <digits>, cscli decisions list -o json,
systemctl restart crowdsec) — validated with visudo -c. Listens on
127.0.0.1 only, reachable through Caddy, and refuses to proceed without
explicit confirmation if no Authelia (local or remote) is configured,
since this page can delete active security bans.

Stdlib-only Python (no framework), matching the RAM-conscious pattern
already used for Easy Asterisk's own web admin. All embedded code
(bash, Python, JS) syntax-checked; the generated sudoers rule
validated with visudo -c -f.

README.md

@@ -67,7 +67,7 @@ a ready-to-copy Caddy config snippet to `~/docker/caddy-snippets/`.
 | Group | Services |
 |-------|---------|
 | `base` | `net-tools`, `ncdu`, `git`, `curl`, `wget`, `htop`, `tree`, `zip`/`unzip`, `ca-certificates`, `gnupg`, `jq`, `rsync`; `glow` (terminal markdown reader, Charm apt repo); Docker CE + Compose plugin; `openssh-server` with GitHub/Launchpad SSH key import, optional password-auth lockdown, and SSH Host aliases; optional NetBird overlay network |
-| `homelab` | `caddy`, `crowdsec`, `authelia`, `homeassistant`, `asterisk`, `asterisk-digital-ocean`, `sunshine` |
+| `homelab` | `caddy`, `crowdsec`, `authelia`, `homeassistant`, `asterisk`, `asterisk-digital-ocean`, `security-dashboard`, `sunshine` |
 | `utilities` | `actualbudget`, `ai-gpu`, `ai-stack`, `archivebox`, `changedetection`, `ddclient`, `filebrowser`, `fmd`, `gatus`, `homebox`, `iopaint`, `joplin`, `koha`, `magicmirror`, `mail-archiver`, `mattermost`, `mealie`, `meshcentral`, `n8n`, `nextcloud`, `ntfy`, `onlyoffice`, `paintplus`, `portainer`, `rustdesk`, `stirling-pdf`, `syncthing`, `traccar`, `unifi`, `uptimekuma`, `vaultwarden`, `watchyourlan`, `watchtower`, `wg-easy` |
 | `media` | `arm`, `audiobookshelf`, `calibre-web`, `emby`, `immich`, `jellyfin`, `lyrion` |
 | `cameras` | `frigate`, `frigate-audio`, `frigate-notify`, `sky-cam` |
@@ -92,6 +92,7 @@ homelab
   homeassistant
   asterisk
   asterisk-digital-ocean
+  security-dashboard
   sunshine
 
 utilities