docs: Add changelog and update role documentation

roles/node_exporter/README.md

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+# Node Exporter
+
+This role installs and configures the Prometheus Node Exporter on target hosts.
+
+## Requirements
+
+None.
+
+## Role Variables
+
+Available variables are listed below, along with default values (see `vars/main.yaml`):
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| `version` | `latest` | The version of Node Exporter to install. |
+| `bind_port` | `9100` | The port Node Exporter will listen on. |
+| `serve` | `localhost` | The address to bind to. |
+| `options` | `""` | Additional command-line options for Node Exporter. |
+| `bin_path` | `/usr/local/bin/node_exporter` | Installation path for the binary. |
+
+## Dependencies
+
+None.
+
+## Example Playbook
+
+```yaml
+- hosts: all
+  roles:
+    - role: node_exporter
+      vars:
+        version: "1.5.0"
+```
+
+## License
+
+MIT