Exclude backup directories and improve YAML formatting

Add exclusion patterns for Nextcloud and Gitea backup directories to avoid
backing up redundant data. Also normalize YAML indentation to 2 spaces for
consistency.

Changes:
- Exclude /opt/nextcloud/backups from backups
- Exclude /opt/gitea/backups from backups
- Add commented suggestions for preview and updater exclusions
- Normalize YAML indentation from 4 spaces to 2 spaces

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

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

config.yaml

@@ -34,6 +34,12 @@ exclude_patterns:
   - "**/__pycache__"
   - "*/node_modules/*"
 
+  - "/opt/nextcloud/backups"
+  #- "/opt/nextcloud/data/appdata_*/preview/*" # Miniatures d'images
+  #- "/opt/nextcloud/updater-*" # Fichiers de mise à jour
+
+  - "/opt/gitea/backups"
+
 # Un seul système de fichiers
 one_file_system: false
 
@@ -81,7 +87,6 @@ commands:
     run:
       - echo "Exécution hook d'erreur"
       - /etc/borgmatic/hooks/ntfy-error.sh
-
 # Commandes PostgreSQL/MySQL si nécessaire
 # postgresql_databases:
 #     - name: all