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/podman/handlers/main.yml

@@ -10,4 +10,9 @@
   systemd:
     name: podman
     state: restarted
-  when: podman_service_enabled | default(true)
+  when: podman_service_enabled | default(true)
+
+- name: reload nftables
+  systemd:
+    name: nftables
+    state: reloaded