feat(observability): add SearXNG, Argos, and Pallas monitoring

- Add SearXNG syslog ingestion and blackbox health probes on miranda
  and rosalind for per-host attributable failure detection
- Scrape Argos MCP application metrics from miranda
- Add Pallas dashboard panels for downstream availability and turn
  error ratios

ansible/pplg/deploy.yml

@@ -200,40 +200,6 @@
   # Grafana
   # ===========================================================================
 
-  - name: Create dashboards directory
-    ansible.builtin.file:
-      path: /var/lib/grafana/dashboards
-      state: directory
-      owner: grafana
-      group: grafana
-      mode: '750'
-
-  - name: Ensure Grafana dashboard provisioning directory exists
-    ansible.builtin.file:
-      path: /etc/grafana/provisioning/dashboards
-      state: directory
-      owner: grafana
-      group: grafana
-      mode: '750'
-
-  - name: Template Grafana dashboard provider (file source → /var/lib/grafana/dashboards)
-    ansible.builtin.template:
-      src: "dashboards_provider.yml.j2"
-      dest: "/etc/grafana/provisioning/dashboards/puck.yaml"
-      owner: grafana
-      group: grafana
-      mode: '640'
-    notify: restart grafana
-
-  - name: Template Puck Services dashboard (Mnemosyne + Pallas + Daedalus)
-    ansible.builtin.template:
-      src: "puck_services_dashboard.json.j2"
-      dest: "/var/lib/grafana/dashboards/puck_services.json"
-      owner: grafana
-      group: grafana
-      mode: '640'
-    notify: restart grafana
-
   - name: Template Grafana main configuration
     ansible.builtin.template:
       src: "grafana.ini.j2"