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were entirely stale content describing a superseded architecture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

@@ -0,0 +1,75 @@
+services:
+  postgres:
+    image: postgres:18
+    container_name: kestra-postgres
+    volumes:
+      - /path/to/kestra/postgres-data:/var/lib/postgresql
+    environment:
+      POSTGRES_DB: ${POSTGRES_DB}
+      POSTGRES_USER: ${POSTGRES_USER}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
+    restart: unless-stopped
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -d $${POSTGRES_DB} -U $${POSTGRES_USER}"]
+      interval: 30s
+      timeout: 10s
+      retries: 10
+    networks:
+      - kestra-net
+
+  kestra:
+    image: kestra/kestra:latest
+    container_name: kestra
+    pull_policy: always
+    # Kestra, by default, has a termination grace period of 5m. We need to wait a little more to be sure no active tasks are running.
+    stop_grace_period: 6m
+    # Note that this setup with a root user is intended for development purpose.
+    # Our base image runs without root, but the Docker Compose implementation needs root to access the Docker socket
+    user: "root"
+    restart: unless-stopped
+    command: server standalone
+    volumes:
+      - /path/to/kestra/kestra-data:/app/storage
+      - /var/run/docker.sock:/var/run/docker.sock
+      - /tmp/kestra-wd:/tmp/kestra-wd
+      # Mounted read-only so Kestra flows can drive the ansible repo directly
+      - /path/to/repos/ansible:/opt/repos/ansible:ro
+      - /path/to/ansible-venv:/home/user/ansible-venv:ro
+      - /path/to/ssh-keys:/home/user/.ssh:ro
+    environment:
+      KESTRA_CONFIGURATION: |
+        datasources:
+          postgres:
+            url: jdbc:postgresql://postgres:5432/kestra
+            driverClassName: org.postgresql.Driver
+            username: ${POSTGRES_USER}
+            password: ${POSTGRES_PASSWORD}
+        kestra:
+          server:
+            basic-auth:
+              username: ${USERNAME}
+              password: ${PASSWORD}
+          repository:
+            type: postgres
+          storage:
+            type: local
+            local:
+              base-path: "/app/storage"
+          queue:
+            type: postgres
+          tasks:
+            tmp-dir:
+              path: /tmp/kestra-wd/tmp
+          url: http://localhost:8080/
+    ports:
+      - "${HTTP_PORT}:8080"
+      - "8081:8081"
+    depends_on:
+      postgres:
+        condition: service_started
+    networks:
+      - kestra-net
+
+networks:
+  kestra-net:
+    external: true