feat: enable Watchtower auto-updates for all application services

Add missing Watchtower labels to:
- net_umami: Analytics service
- dev_gitea_runner: CI/CD runner
- sexy_api: Directus CMS backend
- util_linkwarden_meilisearch: Search engine

All application services now have automatic updates enabled.
Critical infrastructure (postgres, redis, traefik) intentionally
excluded from auto-updates for stability.

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

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

dev/compose.yaml

@@ -88,6 +88,9 @@ services:
       DOCKER_HOST: unix:///var/run/docker.sock
     networks:
       - compose_network
+    labels:
+      # Watchtower
+      - "com.centurylinklabs.watchtower.enable=${WATCHTOWER_LABEL_ENABLE}"
 
   # Coolify - Self-hosted deployment platform
   coolify: