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/searxng/deploy.yml

@@ -57,78 +57,3 @@
       project_src: "{{searxng_directory}}"
       state: present
       pull: always
-
-  # ===========================================================================
-  # OAuth2-Proxy Sidecar
-  # Note: Each host supports at most one OAuth2-Proxy sidecar instance
-  # (binary shared at /usr/local/bin/oauth2-proxy, unique systemd unit per service)
-  # ===========================================================================
-  - name: Create oauth2-proxy directory
-    ansible.builtin.file:
-      path: "{{ searxng_oauth2_proxy_dir }}"
-      owner: root
-      group: root
-      state: directory
-      mode: '0755'
-
-  - name: Download oauth2-proxy binary
-    ansible.builtin.get_url:
-      url: "https://github.com/oauth2-proxy/oauth2-proxy/releases/download/v{{ searxng_oauth2_proxy_version }}/oauth2-proxy-v{{ searxng_oauth2_proxy_version }}.linux-amd64.tar.gz"
-      dest: "/tmp/oauth2-proxy-v{{ searxng_oauth2_proxy_version }}.tar.gz"
-      mode: '0644'
-
-  - name: Extract oauth2-proxy binary
-    ansible.builtin.unarchive:
-      src: "/tmp/oauth2-proxy-v{{ searxng_oauth2_proxy_version }}.tar.gz"
-      dest: /tmp
-      remote_src: true
-      creates: "/tmp/oauth2-proxy-v{{ searxng_oauth2_proxy_version }}.linux-amd64/oauth2-proxy"
-
-  - name: Install oauth2-proxy binary
-    ansible.builtin.copy:
-      src: "/tmp/oauth2-proxy-v{{ searxng_oauth2_proxy_version }}.linux-amd64/oauth2-proxy"
-      dest: /usr/local/bin/oauth2-proxy
-      owner: root
-      group: root
-      mode: '0755'
-      remote_src: true
-
-  - name: Template oauth2-proxy configuration
-    ansible.builtin.template:
-      src: oauth2-proxy-searxng.cfg.j2
-      dest: "{{ searxng_oauth2_proxy_dir }}/oauth2-proxy.cfg"
-      owner: root
-      group: root
-      mode: '0600'
-    notify: restart oauth2-proxy-searxng
-
-  - name: Template oauth2-proxy systemd service
-    ansible.builtin.template:
-      src: oauth2-proxy-searxng.service.j2
-      dest: /etc/systemd/system/oauth2-proxy-searxng.service
-      owner: root
-      group: root
-      mode: '0644'
-    notify:
-      - reload systemd
-      - restart oauth2-proxy-searxng
-
-  # ===========================================================================
-  # Service Management
-  # ===========================================================================
-  - name: Enable and start OAuth2-Proxy service
-    ansible.builtin.systemd:
-      name: oauth2-proxy-searxng
-      enabled: true
-      state: started
-      daemon_reload: true
-
-  handlers:
-  - name: reload systemd
-    ansible.builtin.systemd:
-      daemon_reload: true
-
-  - name: restart oauth2-proxy-searxng
-    ansible.builtin.systemd:
-      name: oauth2-proxy-searxng
-      state: restarted