feat(unbound): add prometheus exporter, dashboard, fix socket buffer sysctl

roles/unbound/tasks/exporter.yml

@@ -0,0 +1,35 @@
+---
+# Prometheus unbound exporter (optional, gated by unbound_exporter_enabled).
+# Scrapes unbound-control stats_noreset over the local control interface.
+
+- name: Assert exporter is supported (Arch Linux only)
+  ansible.builtin.assert:
+    that: ansible_facts['os_family'] == 'Archlinux'
+    fail_msg: |
+      The unbound exporter (prometheus-unbound-exporter) is only packaged for
+      Arch Linux. It is not available in Debian/Ubuntu repositories.
+    success_msg: "Unbound exporter supported"
+
+- name: Load OS-specific exporter variables
+  ansible.builtin.include_vars: archlinux.yml
+
+- name: Install prometheus-unbound-exporter
+  ansible.builtin.package:
+    name: "{{ unbound_exporter_package }}"
+    state: present
+
+- name: Deploy exporter environment file
+  ansible.builtin.template:
+    src: exporter-env.conf.j2
+    dest: "{{ unbound_exporter_args_file }}"
+    owner: root
+    group: root
+    mode: "0644"
+  notify: Restart unbound exporter
+
+- name: Enable and start prometheus-unbound-exporter
+  ansible.builtin.systemd:
+    name: "{{ unbound_exporter_service }}"
+    enabled: true
+    state: started
+    daemon_reload: true