Add self-contained Docker Compose stacks for pivoine.art infrastructure

Migrated 11 services from monolithic docker-compose project into independent stacks,
each with dedicated databases, minimal .env configuration, and bind-mount data volumes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

watchtower/compose.yml

@@ -0,0 +1,22 @@
+---
+services:
+  watchtower:
+    image: containrrr/watchtower:latest
+    container_name: watchtower
+    environment:
+      DOCKER_API_VERSION: "1.44"
+      WATCHTOWER_POLL_INTERVAL: 300
+      WATCHTOWER_LABEL_ENABLE: "true"
+      WATCHTOWER_CLEANUP: "true"
+      WATCHTOWER_INCLUDE_STOPPED: "false"
+      WATCHTOWER_INCLUDE_RESTARTING: "true"
+      WATCHTOWER_RUN_ONCE: "false"
+      WATCHTOWER_NOTIFICATIONS: ${NOTIFICATIONS:-}
+      WATCHTOWER_NOTIFICATION_URL: ${NOTIFICATION_URL:-}
+      WATCHTOWER_LOG_LEVEL: info
+      WATCHTOWER_ROLLING_RESTART: "false"
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+    restart: always
+    labels:
+      - "com.centurylinklabs.watchtower.enable=true"