refactor: use $DOMAIN env var instead of hardcoded lazyworkhorse.net

Replace all hardcoded lazyworkhorse.net references in compose files
with ${DOMAIN} variable substitution. Create .env.production and
.env.staging environment files. Update Makefile with ENV selection
(--env-file support) and staging/production targets.

Changes:
- All 13 compose YAML files: lazyworkhorse.net -> ${DOMAIN}
- New .env.production (DOMAIN=lazyworkhorse.net)
- New .env.staging (DOMAIN=staging.lazyworkhorse.net)
- Makefile: ENV var, --env-file flag, staging/production targets
- Gitea redirect regex updated for variable substitution
- CI workflow checkout URLs left hardcoded (infrastructure refs)
- Dockerfile SSH host refs left hardcoded (infrastructure refs)

Deploy: make ENV=staging all_up  or  make staging
        make ENV=production all_up  or  make production

cloudstorage/compose.yml

@@ -17,8 +17,8 @@ services:
       - MYSQL_PASSWORD=${NEXTCLOUD_MYSQL_PASSWORD}
       # Reverse Proxy Overrides (Crucial for HTTPS behind Traefik)
       - OVERWRITEPROTOCOL=https
-      - OVERWRITECLIURL=https://cloud.lazyworkhorse.net
-      - NEXTCLOUD_TRUSTED_DOMAINS=cloud.lazyworkhorse.net
+      - OVERWRITECLIURL=https://cloud.${DOMAIN}
+      - NEXTCLOUD_TRUSTED_DOMAINS=cloud.${DOMAIN}
     volumes:
       - /mnt/HoardingCow_docker_data/NextCloud/data:/var/www/html:rw
     depends_on:
@@ -27,12 +27,12 @@ services:
       - "traefik.enable=true"
 
       # Router for HTTP -> HTTPS Redirection (Matching your Gitea style)
-      - "traefik.http.routers.nextcloud-http.rule=Host(`cloud.lazyworkhorse.net`)"
+      - "traefik.http.routers.nextcloud-http.rule=Host(`cloud.${DOMAIN}`)"
       - "traefik.http.routers.nextcloud-http.entrypoints=web"
       - "traefik.http.routers.nextcloud-http.middlewares=redirect-to-https"
 
       # Router for HTTPS
-      - "traefik.http.routers.nextcloud-https.rule=Host(`cloud.lazyworkhorse.net`)"
+      - "traefik.http.routers.nextcloud-https.rule=Host(`cloud.${DOMAIN}`)"
       - "traefik.http.routers.nextcloud-https.entrypoints=websecure"
       - "traefik.http.routers.nextcloud-https.tls=true"
       - "traefik.http.routers.nextcloud-https.tls.certresolver=njalla"