node_exporter: retire standalone role (replaced by Alloy embedded)

Embedded prometheus.exporter.unix in Alloy has been pushing identical
metrics fleet-wide since 2026-05-21 cutover; the standalone binary
and systemd service have been removed from each host. Drops the
role + site.yml entry so future deploys don't reinstate them.

See homelab-docs/docs/audit/alloy-consolidation-2026-05-21.md.

roles/node_exporter/handlers/main.yml

@@ -1,6 +0,0 @@
----
-- name: restart node_exporter
-  systemd:
-    name: node_exporter
-    state: restarted
-    daemon_reload: yes

roles/node_exporter/tasks/main.yml

@@ -1,120 +0,0 @@
----
-- name: Check if node_exporter is installed
-  stat:
-    path: /usr/local/bin/node_exporter
-  register: ne_bin
-
-- name: Set architecture
-  set_fact:
-    ne_arch: "{{ 'arm64' if ansible_architecture == 'aarch64' else 'amd64' }}"
-
-- name: Get latest node_exporter version
-  uri:
-    url: https://api.github.com/repos/prometheus/node_exporter/releases/latest
-    return_content: yes
-  register: ne_release
-  when: not ne_bin.stat.exists
-
-- name: Set node_exporter version
-  set_fact:
-    ne_version: "{{ ne_release.json.tag_name | regex_replace('^v', '') }}"
-  when: not ne_bin.stat.exists
-
-- name: Download node_exporter
-  get_url:
-    url: "https://github.com/prometheus/node_exporter/releases/download/v{{ ne_version }}/node_exporter-{{ ne_version }}.linux-{{ ne_arch }}.tar.gz"
-    dest: /tmp/node_exporter.tar.gz
-  when: not ne_bin.stat.exists
-
-- name: Extract node_exporter
-  unarchive:
-    src: /tmp/node_exporter.tar.gz
-    dest: /tmp/
-    remote_src: yes
-  when: not ne_bin.stat.exists
-
-- name: Install node_exporter binary
-  copy:
-    src: "/tmp/node_exporter-{{ ne_version }}.linux-{{ ne_arch }}/node_exporter"
-    dest: /usr/local/bin/node_exporter
-    owner: root
-    group: root
-    mode: '0755'
-    remote_src: yes
-  when: not ne_bin.stat.exists
-  notify: restart node_exporter
-
-- name: Create node_exporter user
-  user:
-    name: node_exporter
-    system: yes
-    shell: /usr/sbin/nologin
-    create_home: no
-
-- name: Deploy node_exporter systemd service
-  copy:
-    content: |
-      [Unit]
-      Description=Prometheus Node Exporter
-      After=network-online.target
-      Wants=network-online.target
-
-      [Service]
-      User=node_exporter
-      Group=node_exporter
-      Type=simple
-      ExecStart=/usr/local/bin/node_exporter --collector.textfile.directory=/var/lib/node_exporter/textfile
-      Restart=on-failure
-      RestartSec=5
-
-      [Install]
-      WantedBy=multi-user.target
-    dest: /etc/systemd/system/node_exporter.service
-    owner: root
-    group: root
-    mode: '0644'
-  notify: restart node_exporter
-
-- name: Create textfile collector directory
-  file:
-    path: /var/lib/node_exporter/textfile
-    state: directory
-    owner: node_exporter
-    group: node_exporter
-    mode: '0755'
-
-- name: Deploy CPU temperature collector script
-  copy:
-    content: |
-      #!/bin/bash
-      TEMP=$(vcgencmd measure_temp 2>/dev/null | grep -oP '[0-9.]+')
-      if [ -n "$TEMP" ]; then
-        echo "# HELP node_cpu_temperature_celsius CPU temperature from vcgencmd"
-        echo "# TYPE node_cpu_temperature_celsius gauge"
-        echo "node_cpu_temperature_celsius $TEMP"
-      fi > /var/lib/node_exporter/textfile/cpu_temp.prom
-    dest: /usr/local/bin/collect-cpu-temp.sh
-    mode: '0755'
-
-- name: Schedule CPU temperature collection (every minute)
-  cron:
-    name: "node_exporter cpu temp"
-    user: node_exporter
-    job: "/usr/local/bin/collect-cpu-temp.sh"
-
-- name: Run initial temperature collection
-  command: /usr/local/bin/collect-cpu-temp.sh
-  changed_when: false
-
-- name: Enable and start node_exporter
-  systemd:
-    name: node_exporter
-    enabled: yes
-    state: started
-    daemon_reload: yes
-
-- name: Clean up download
-  file:
-    path: /tmp/node_exporter.tar.gz
-    state: absent
-  when: not ne_bin.stat.exists