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_board/CMakeLists.txt

@@ -1,2 +1,3 @@
 idf_component_register(SRCS "aes67_board.c"
-                       INCLUDE_DIRS "include")
+                       INCLUDE_DIRS "include"
+                       REQUIRES esp_eth)