feat: add Go-based HarborForge monitor client

- collect CPU, memory, disk, swap, load, and uptime telemetry
- detect nginx and list /etc/nginx/sites-enabled entries
- send heartbeat-v2 payload with API key auth
- provide install script, config example, and systemd unit

scripts/install.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+BIN_NAME="harborforge-monitor"
+INSTALL_DIR="/usr/local/bin"
+CONFIG_DIR="/etc/harborforge-monitor"
+SERVICE_PATH="/etc/systemd/system/harborforge-monitor.service"
+
+if [[ "${EUID}" -ne 0 ]]; then
+  echo "Please run as root (or via sudo)." >&2
+  exit 1
+fi
+
+mkdir -p "${CONFIG_DIR}"
+
+pushd "${ROOT_DIR}" >/dev/null
+go build -o "${BIN_NAME}" ./cmd/harborforge-monitor
+install -m 0755 "${BIN_NAME}" "${INSTALL_DIR}/${BIN_NAME}"
+install -m 0644 systemd/harborforge-monitor.service "${SERVICE_PATH}"
+if [[ ! -f "${CONFIG_DIR}/config.json" ]]; then
+  install -m 0644 config.example.json "${CONFIG_DIR}/config.json"
+fi
+systemctl daemon-reload
+systemctl enable --now harborforge-monitor
+popd >/dev/null
+
+echo "Installed ${BIN_NAME}. Edit ${CONFIG_DIR}/config.json and restart the service if needed."