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were entirely stale content describing a superseded architecture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

@@ -0,0 +1,34 @@
+services:
+  kopia:
+    image: kopia/kopia:latest
+    container_name: kopia
+    restart: unless-stopped
+    user: "0:0"
+    hostname: "docker-host"
+    ports:
+      - "${HTTP_PORT}:51515"
+    command:
+      - server
+      - start
+      - --address=0.0.0.0:51515
+      - --tls-cert-file=/tls/kopia.crt
+      - --tls-key-file=/tls/kopia.key
+      - --server-username=${USERNAME}
+      - --server-password=${SECRET_PASSWORD}
+      - --disable-csrf-token-checks
+    environment:
+      TZ: ${TZ}
+      KOPIA_PASSWORD: ${SECRET_PASSWORD}
+    volumes:
+      - /path/to/backup-drive/kopia-repo:/repository # External drive for repository
+      - /path/to/backup-drive/kopia-cache:/cache
+      - /path/to/backup-drive/kopia-config:/app/config
+      - /path/to/backup-drive/kopia-tls:/tls:ro
+      - /path/to/docker-volumes:/apps:ro # Read-only access to docker volumes
+      - /path/to/docker-volumes:/restore
+    networks:
+      - kopia-net
+
+networks:
+  kopia-net:
+    external: true