feat: adguard-register — auto DNS registration agent for AdGuard Home

Registers {hostname}.home.dustin.coffee → host IP on boot via AdGuard Home API.
Deploy to any LXC/VM with ./install.sh — supports root (system service),
sudo user (system via sudo), and unprivileged user (systemd --user or crontab).

Files:
- adguard-register.sh — detects hostname+IP, idempotent create/update
- install.sh — deployment script with auto-detection of install method
- uninstall.sh — removes service and binary
- README.md — full documentation

Tested across 24 hosts (LXCs and VMs) on a 172.20.0.0/16 home lab network.

uninstall.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+# uninstall.sh — remove adguard-register from this host
+# Run as root (or with sudo): ./uninstall.sh
+
+set -euo pipefail
+
+INSTALL_PATH="/usr/local/bin/adguard-register"
+SERVICE_PATH="/etc/systemd/system/adguard-register.service"
+
+if [ "$(id -u)" -ne 0 ]; then
+    echo "ERROR: This script must be run as root (use sudo)"
+    exit 1
+fi
+
+echo "=== Uninstalling adguard-register ==="
+
+# Stop and disable service (ignore errors if not installed)
+systemctl stop adguard-register.service 2>/dev/null || true
+systemctl disable adguard-register.service 2>/dev/null || true
+rm -f "${SERVICE_PATH}"
+systemctl daemon-reload
+echo "→ Removed systemd service"
+
+# Remove script
+rm -f "${INSTALL_PATH}"
+echo "→ Removed ${INSTALL_PATH}"
+
+echo ""
+echo "=== Uninstall complete ==="
+echo "NOTE: Existing DNS rewrites in AdGuard Home were NOT removed."
+echo "To clean up entries, use the AdGuard Home web UI or API directly."