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were entirely stale content describing a superseded architecture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/n8n/docker-compose.yaml

@@ -0,0 +1,64 @@
+services:
+  n8n:
+    image: n8nio/n8n:latest
+    container_name: n8n
+    restart: unless-stopped
+    security_opt:
+      - no-new-privileges:true
+    environment:
+      - PUID=${PUID}
+      - PGID=${PGID}
+      - TZ=${TZ}
+      - GENERIC_TIMEZONE=${TZ}
+      - N8N_HOST=${N8N_HOST}
+      - N8N_PORT=${N8N_PORT}
+      - N8N_PROTOCOL=https
+      - DB_TYPE=postgresdb
+      - DB_POSTGRESDB_HOST=postgres
+      - DB_POSTGRESDB_PORT=5432
+      - DB_POSTGRESDB_DATABASE=n8n
+      - DB_POSTGRESDB_USER=n8n
+      - DB_POSTGRESDB_PASSWORD=${N8N_POSTGRES_PASSWORD}
+      - N8N_BASIC_AUTH_ACTIVE=true
+      - N8N_BASIC_AUTH_USER=${N8N_USER}
+      - N8N_BASIC_AUTH_PASSWORD=${N8N_BASIC_AUTH_PASSWORD}
+      - WEBHOOK_URL=https://${N8N_HOST}
+      - N8N_ENFORCE_SETTINGS_FILE_PERMISSIONS=true
+    volumes:
+      - /path/to/n8n/data:/home/node/
+    ports:
+      - ${N8N_PORT}:5678
+    depends_on:
+      - postgres
+    networks:
+      - n8n-net
+
+  postgres:
+    image: postgres:latest
+    container_name: n8n-postgres
+    restart: unless-stopped
+    security_opt:
+      - no-new-privileges:true
+    environment:
+      POSTGRES_USER: n8n
+      POSTGRES_PASSWORD: ${N8N_POSTGRES_PASSWORD}
+      POSTGRES_DB: n8n
+    volumes:
+      - /path/to/n8n/postgres_data:/var/lib/postgresql
+    ports:
+      - "127.0.0.1:${POSTGRES_PORT}:5432"
+    networks:
+      - n8n-net
+
+  adminer:
+    image: adminer:latest
+    container_name: adminer
+    restart: unless-stopped
+    ports:
+      - "127.0.0.1:${ADMINER_PORT}:8080"
+    networks:
+      - n8n-net
+
+networks:
+  n8n-net:
+    external: true