feat(bind9): support systemd drop-ins

Keep role configuration namespaced and allow hosts to customize systemd startup.

Co-authored-by: Copilot <copilot@github.com>

handlers/main.yaml

@@ -2,6 +2,6 @@
 
 - name: Restart named
   ansible.builtin.systemd:
-    name: "{{ bind_service_name }}"
+    name: "{{ bind9_service_name }}"
     state: restarted
     daemon_reload: true