Docs-as-code: full deploy configs, compose stacks, and DR guide

- Add root README and docs/ (architecture, hosts, disaster-recovery, operations)
- Add compose/ for superset, forgejo, lam, cadvisor; unified deploy compose
- Add scripts/deploy (deploy-atc-docker01.sh, container inventory export)
- Add inventory/containers-atc-docker01.json snapshot
- Add config READMEs for kafka and airflow; .env.example; expand .gitignore
- Sync atclab helper scripts; update homepage/superset compose with env support

config/superset/docker-compose.yaml

@@ -5,8 +5,10 @@ services:
     restart: unless-stopped
     ports:
       - "8088:8088"
+    env_file:
+      - ../../.env
     environment:
-      - SUPERSET_SECRET_KEY=your-secret-key-here
+      - SUPERSET_SECRET_KEY=${SUPERSET_SECRET_KEY:-change-me}
       - SUPERSET_LOAD_EXAMPLES=no
     volumes:
       - ./superset_config.py:/app/pythonpath/superset_config.py