Restructure compose mirror: stacks/ grouped by purpose, not by host

Replaces rocky-docker-lxc/, caddy-vm/, monitoring-vm/, and automation/
with a single stacks/ tree grouped by function (identity-and-security,
platform, media, productivity, dev-tools) - 55 stacks total, every one
a real directory in the private repos today.

Resolves all outstanding drift: adds Wazuh (previously entirely
missing), Firefly III and Postiz (never mirrored), the internal-zone
Caddy instance and the Cron Scheduler's separate NocoDB instance
(both previously conflated with their counterparts under one shared
folder); renames Calibre-Web to calibre-web-automated and splits
Kodi-MariaDB into kodi + mariadb-latest to match what the private
repos actually run now; drops the decommissioned NetBox stack.

Also removes automation/iac/old-content/ and
automation/ansible/old-playbooks/ in the same pass - both folders
were entirely stale content describing a superseded architecture
(GitLab instead of Gitea, HAProxy+mTLS SSO instead of the current
Caddy+Authentik setup), now replaced by docs/iac-pipeline.md.

stacks/media/audiobookshelf/docker-compose.yaml

@@ -0,0 +1,27 @@
+services:
+  audiobookshelf:
+    image: ghcr.io/advplyr/audiobookshelf:latest
+    container_name: audiobookshelf
+    user: "${PUID}:${PGID}"
+    environment:
+      - TZ=${TZ}
+    ports:
+      - ${HTTP_PORT}:80
+    volumes:
+      - /path/to/audiobookshelf/config:/config
+      - /path/to/audiobookshelf/metadata:/metadata
+      - /path/to/data/media/audiobooks:/audiobooks
+      - /path/to/data/media/podcasts:/podcasts
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD-SHELL", "wget -qO- http://localhost:80/ || exit 1"]
+      interval: 15s
+      timeout: 5s
+      retries: 5
+      start_period: 20s
+    networks:
+      - audiobookshelf-net
+
+networks:
+  audiobookshelf-net:
+    external: true