Initial commit: DHCP whitelist service for direct link connections

Features:
- Docker-based DHCP server with MAC address whitelisting
- Binds to specific ethernet interface only
- NO DNS/gateway advertised (direct link only, not a router)
- Configurable network parameters (subnet, DHCP range, lease times)
- Systemd service integration for Arch/Manjaro
- Test environment with isolated network (172.20.0.0/24)
- Auto-configuration script to detect network settings
- Complete Makefile with management targets

Security:
- Only responds to whitelisted MAC addresses
- deny unknown-clients configuration
- Runs in Docker container for isolation

Configuration:
- Copy .example files to create your config
- interface.conf: Network interface to bind to
- whitelist.conf: Allowed MAC addresses
- network.conf: Network parameters (optional)

systemd/dhcp-whitelist.service

@@ -0,0 +1,29 @@
+[Unit]
+Description=DHCP Whitelist Service
+After=network.target docker.service
+Requires=docker.service
+
+[Service]
+Type=simple
+Restart=always
+RestartSec=10
+WorkingDirectory=/opt/dhcp-whitelist
+Environment="CONFIG_DIR=/etc/dhcp-whitelist"
+
+# Pre-start: Build the image
+ExecStartPre=/usr/bin/docker-compose build
+
+# Start the service
+ExecStart=/usr/bin/docker-compose up
+
+# Stop the service
+ExecStop=/usr/bin/docker-compose down
+
+# Reload config by restarting containers
+ExecReload=/usr/bin/docker-compose restart
+
+StandardOutput=journal
+StandardError=journal
+
+[Install]
+WantedBy=multi-user.target