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were entirely stale content describing a superseded architecture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/productivity/firefly-iii/docker-compose.yaml

@@ -0,0 +1,49 @@
+services:
+  fireflyiii:
+    image: fireflyiii/core:latest
+    container_name: fireflyiii_app
+    restart: unless-stopped
+    depends_on:
+      - mariadb
+    env_file:
+      - .env.secrets   # APP_KEY, DB_PASSWORD — never committed
+    environment:
+      - DB_CONNECTION=mysql
+      - DB_HOST=mariadb
+      - DB_PORT=3306
+      - DB_DATABASE=fireflyiii
+      - DB_USERNAME=fireflyuser
+      - TZ=${TZ}
+      - TRUSTED_PROXIES=**
+      - APP_ENV=production
+      - AUTHENTICATION_GUARD=${AUTHENTICATION_GUARD}
+      - AUTHENTICATION_GUARD_HEADER=${AUTHENTICATION_GUARD_HEADER}
+    volumes:
+      - /path/to/fireflyiii/firefly_iii_upload:/var/www/html/storage/upload
+    ports:
+      - "${HTTP_PORT}:8080"
+    networks:
+      - firefly-net
+
+  mariadb:
+    image: mariadb:latest
+    container_name: fireflyiii_db
+    restart: unless-stopped
+    env_file:
+      - .env.secrets   # MYSQL_PASSWORD, MYSQL_ROOT_PASSWORD — never committed
+    environment:
+      - PUID=${PUID}
+      - PGID=${PGID}
+      - TZ=${TZ}
+      - MYSQL_DATABASE=fireflyiii
+      - MYSQL_USER=fireflyuser
+    volumes:
+      - /path/to/fireflyiii/firefly_iii_db:/config
+    ports:
+      - "${DB_PORT}:3306"
+    networks:
+      - firefly-net
+
+networks:
+  firefly-net:
+    external: true