feat: add dockcheck auto-update labels to remaining services

Add mag37.dockcheck.update labels to enable automated container update monitoring for:
- Gotify iOS assistant service
- Karakeep (Hoarder) bookmark manager and all components (Chrome, Meilisearch)
- MMDL task management service
- Postiz social media scheduler and all components (PostgreSQL, Redis)

This completes the rollout of dockcheck labels across all Docker services for consistent update monitoring.

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

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

roles/docker/templates/mmdl-compose.yml.j2

@@ -17,6 +17,7 @@ services:
       glance.url: https://{{ subdomains.tasks }}/
       glance.description: Task and calendar management
       glance.id: mmdl
+      mag37.dockcheck.update: true
 
   mmdl_db:
     image: mysql:8.0