fix(monitoring): exporter auth and reload fixes

- postgres: use lib/pq conninfo DATA_SOURCE_NAME; the postgresql:// URL
  form broke on special chars in the password (net/url: invalid userinfo)
- nginx: flush handlers after deploying stub_status so nginx reloads
  before the exporter starts scraping
- valkey: drop invalid +arcount command from the exporter ACL set
  (Valkey aborted startup parsing the ACL file)

roles/nginx/tasks/exporter.yml

@@ -17,6 +17,9 @@
     mode: "0644"
   notify: Reload nginx
 
+- name: Flush handlers to reload nginx with stub_status
+  ansible.builtin.meta: flush_handlers
+
 - name: Deploy exporter environment file
   ansible.builtin.template:
     src: exporter-env.conf.j2