feat: integrate Facefusion into AI stack

Added Facefusion face swapping service to the AI stack:

**Configuration:**
- URL: https://facefusion.ai.pivoine.art
- Image: facefusion/facefusion:3.5.0-cpu
- Port: 7865
- Container: ai_facefusion
- Volume: ai_facefusion_data
- HTTP Basic Auth protection
- CPU execution mode (GPU when available)

**Changes:**
- Added facefusion service to ai/compose.yaml
- Added AI_FACEFUSION_* env vars to arty.yml
- Created ai_facefusion_data volume
- Removed old standalone facefusion stack
- Removed ai/README-export.md and ai/webui-export.py

Facefusion will run on CPU until GPU server is available.

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

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

ai/facefusion.yaml

@@ -0,0 +1,37 @@
+services:
+  facefusion:
+    image: ${FACEFUSION_IMAGE:-facefusion/facefusion:3.5.0-cpu}
+    container_name: ${FACEFUSION_COMPOSE_PROJECT_NAME}_app
+    restart: unless-stopped
+    environment:
+      TZ: ${TIMEZONE:-Europe/Berlin}
+      # Force CPU execution on VPS (no GPU available)
+      FACEFUSION_EXECUTION_PROVIDERS: ${FACEFUSION_EXECUTION_PROVIDERS:-cpu}
+    volumes:
+      - facefusion_data:/workspace
+    networks:
+      - compose_network
+    labels:
+      - 'traefik.enable=${FACEFUSION_TRAEFIK_ENABLED}'
+      # HTTP Basic Auth middleware
+      - 'traefik.http.middlewares.${FACEFUSION_COMPOSE_PROJECT_NAME}-auth.basicauth.users=${AUTH_USERS}'
+      # HTTP to HTTPS redirect
+      - 'traefik.http.middlewares.${FACEFUSION_COMPOSE_PROJECT_NAME}-redirect-web-secure.redirectscheme.scheme=https'
+      - 'traefik.http.routers.${FACEFUSION_COMPOSE_PROJECT_NAME}-web.middlewares=${FACEFUSION_COMPOSE_PROJECT_NAME}-redirect-web-secure'
+      - 'traefik.http.routers.${FACEFUSION_COMPOSE_PROJECT_NAME}-web.rule=Host(`${FACEFUSION_TRAEFIK_HOST}`)'
+      - 'traefik.http.routers.${FACEFUSION_COMPOSE_PROJECT_NAME}-web.entrypoints=web'
+      # HTTPS router with auth
+      - 'traefik.http.routers.${FACEFUSION_COMPOSE_PROJECT_NAME}-web-secure.rule=Host(`${FACEFUSION_TRAEFIK_HOST}`)'
+      - 'traefik.http.routers.${FACEFUSION_COMPOSE_PROJECT_NAME}-web-secure.tls.certresolver=resolver'
+      - 'traefik.http.routers.${FACEFUSION_COMPOSE_PROJECT_NAME}-web-secure.entrypoints=web-secure'
+      - 'traefik.http.middlewares.${FACEFUSION_COMPOSE_PROJECT_NAME}-web-secure-compress.compress=true'
+      - 'traefik.http.routers.${FACEFUSION_COMPOSE_PROJECT_NAME}-web-secure.middlewares=${FACEFUSION_COMPOSE_PROJECT_NAME}-auth,${FACEFUSION_COMPOSE_PROJECT_NAME}-web-secure-compress,security-headers@file'
+      # Service
+      - 'traefik.http.services.${FACEFUSION_COMPOSE_PROJECT_NAME}-web-secure.loadbalancer.server.port=7860'
+      - 'traefik.docker.network=${NETWORK_NAME}'
+      # Watchtower
+      - 'com.centurylinklabs.watchtower.enable=${WATCHTOWER_LABEL_ENABLE}'
+
+volumes:
+  facefusion_data:
+    name: ${FACEFUSION_COMPOSE_PROJECT_NAME}_data