feat: add miniPaint stack (paint.pivoine.art)

Added new paint service stack to the docker-compose infrastructure:

- **Paint stack** (paint.pivoine.art):
  - miniPaint: Web-based image editor built from GitHub
  - Multi-stage Docker build clones from https://github.com/viliusle/miniPaint
  - Features: layers, filters, drawing tools, text, shapes support
  - Client-side processing with no server uploads
  - Stateless architecture (no backups needed)

Infrastructure updates:
- Created paint/compose.yaml with Traefik routing and SSL
- Created paint/Dockerfile with Node.js build stage and nginx serve
- Added PAINT environment variables to arty.yml
- Updated compose.yaml include list
- Updated CLAUDE.md documentation

All services integrated with Traefik for SSL termination and include
Watchtower auto-update labels.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

paint/compose.yaml

@@ -0,0 +1,32 @@
+services:
+  paint:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    image: minipaint:latest
+    container_name: ${PAINT_COMPOSE_PROJECT_NAME}_app
+    restart: unless-stopped
+    networks:
+      - compose_network
+    labels:
+      - 'traefik.enable=${PAINT_TRAEFIK_ENABLED}'
+      # HTTP to HTTPS redirect
+      - 'traefik.http.middlewares.${PAINT_COMPOSE_PROJECT_NAME}-redirect-web-secure.redirectscheme.scheme=https'
+      - 'traefik.http.routers.${PAINT_COMPOSE_PROJECT_NAME}-web.middlewares=${PAINT_COMPOSE_PROJECT_NAME}-redirect-web-secure'
+      - 'traefik.http.routers.${PAINT_COMPOSE_PROJECT_NAME}-web.rule=Host(`${PAINT_TRAEFIK_HOST}`)'
+      - 'traefik.http.routers.${PAINT_COMPOSE_PROJECT_NAME}-web.entrypoints=web'
+      # HTTPS router
+      - 'traefik.http.routers.${PAINT_COMPOSE_PROJECT_NAME}-web-secure.rule=Host(`${PAINT_TRAEFIK_HOST}`)'
+      - 'traefik.http.routers.${PAINT_COMPOSE_PROJECT_NAME}-web-secure.tls.certresolver=resolver'
+      - 'traefik.http.routers.${PAINT_COMPOSE_PROJECT_NAME}-web-secure.entrypoints=web-secure'
+      - 'traefik.http.routers.${PAINT_COMPOSE_PROJECT_NAME}-web-secure.middlewares=security-headers@file'
+      # Service
+      - 'traefik.http.services.${PAINT_COMPOSE_PROJECT_NAME}-web-secure.loadbalancer.server.port=80'
+      - 'traefik.docker.network=${NETWORK_NAME}'
+      # Watchtower
+      - 'com.centurylinklabs.watchtower.enable=${WATCHTOWER_LABEL_ENABLE}'
+
+networks:
+  compose_network:
+    name: ${NETWORK_NAME}
+    external: true