feat(media): add Immich photo/video management service

- Add immich_server, immich_ml, and immich_postgres services
- Use dedicated PostgreSQL with vector extensions (vectorchord + pgvectors)
- Connect to core Redis for job queues
- Configure Traefik routing for immich.media.pivoine.art
- Add backup volumes and plan for Backrest (daily at 12:00)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

core/compose.yaml

@@ -88,6 +88,8 @@ services:
       - backup_dev_gitea_config:/volumes/dev_gitea_config:ro
       - backup_dev_gitea_runner_data:/volumes/dev_gitea_runner_data:ro
       - backup_dev_coolify_data:/volumes/dev_coolify_data:ro
+      - backup_media_immich_postgres_data:/volumes/immich_postgres_data:ro
+      - backup_media_immich_upload:/volumes/immich_upload:ro
 
     environment:
       TZ: ${TIMEZONE:-Europe/Berlin}
@@ -200,3 +202,9 @@ volumes:
   backup_dev_coolify_data:
     name: dev_coolify_data
     external: true
+  backup_media_immich_postgres_data:
+    name: media_immich_postgres_data
+    external: true
+  backup_media_immich_upload:
+    name: media_immich_upload
+    external: true