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)

Dockerfile

@@ -0,0 +1,18 @@
+FROM alpine:3.19
+
+RUN apk add --no-cache \
+    dhcp \
+    bash \
+    iproute2
+
+RUN mkdir -p /var/lib/dhcp /etc/dhcp /run/dhcp
+
+COPY dhcp/entrypoint.sh /entrypoint.sh
+COPY dhcp/dhcpd.conf.template /etc/dhcp/dhcpd.conf.template
+
+RUN chmod +x /entrypoint.sh && \
+    touch /var/lib/dhcp/dhcpd.leases
+
+EXPOSE 67/udp
+
+ENTRYPOINT ["/entrypoint.sh"]