Step 1: Ethernet up (IP101/RMII), DHCP, link and IP logged

- aes67_board: Waveshare ESP32-P4-ETH pin profile and EMAC + IP101 driver
  install (PHY addr 1, reset GPIO51, ref clock in on GPIO50).
- aes67_net: Ethernet netif with DHCP client; logs link up/down (speed,
  duplex, MAC) and the DHCP lease.
- Verified on board: 100 Mbps full duplex, DHCP lease in ~8 s, ping
  0% loss, ~0.2 ms RTT.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

components/aes67_net/include/aes67_net.h

@@ -3,5 +3,7 @@
 #pragma once
 
 #include "esp_err.h"
+#include "esp_eth_driver.h"
 
-esp_err_t aes67_net_init(void);
+// Attach a netif (DHCP client) to the Ethernet driver and start it. Logs link and IP events.
+esp_err_t aes67_net_init(esp_eth_handle_t eth);