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/postiz-compose.yml.j2

@@ -38,6 +38,7 @@ services:
       glance.url: https://{{ subdomains.post }}/
       glance.description: Social media scheduler
       glance.id: postiz
+      mag37.dockcheck.update: true
  
   postiz-postgres:
     image: postgres:14.5
@@ -57,6 +58,7 @@ services:
     labels:
       glance.parent: postiz
       glance.name: DB
+      mag37.dockcheck.update: true
   postiz-redis:
     image: redis:7.2
     container_name: postiz-redis
@@ -71,6 +73,7 @@ services:
     labels:
       glance.parent: postiz
       glance.name: Redis
+      mag37.dockcheck.update: true