Fix Nextcloud DNS resolution and implement systemd cron for background jobs

- Enable IP forwarding in security playbook (net.ipv4.ip_forward = 1)
- Add podman network firewall rules to fix container DNS/HTTPS access
- Implement systemd timer for reliable Nextcloud background job execution
- Add database optimization tasks (indices, bigint conversion, mimetypes)
- Configure maintenance window (04:00 UTC) and phone region (NO)
- Add security headers (X-Robots-Tag, X-Permitted-Cross-Domain-Policies)
- Create Nextcloud removal playbook for clean uninstall
- Fix nftables interface matching (podman0 vs podman+)

Root cause: nftables FORWARD chain blocked container egress traffic
Solution: Explicit firewall rules for podman0 bridge interface

roles/nextcloud/defaults/main.yml

@@ -67,6 +67,20 @@ nextcloud_overwriteprotocol: "https"
 nextcloud_php_memory_limit: "512M"
 nextcloud_php_upload_limit: "512M"
 
+# =================================================================
+# Background Jobs Configuration
+# =================================================================
+
+nextcloud_background_jobs_mode: "cron"  # Options: ajax, webcron, cron
+nextcloud_cron_interval: "5min"  # How often cron runs (systemd timer)
+
+# =================================================================
+# Maintenance Configuration
+# =================================================================
+
+nextcloud_maintenance_window_start: 4  # Start hour (UTC) for maintenance window
+nextcloud_default_phone_region: "NO"  # Default phone region code (ISO 3166-1 alpha-2)
+
 # =================================================================
 # Caddy Integration
 # =================================================================