Step 2a (2/2): LLDP transmit, switch shows name and IP

- aes67_net/lldp.c: IEEE 802.1AB LLDPDU sent as a raw frame with
  esp_eth_transmit every 30 s (TTL 120 s) and immediately on a new IP
  or hostname change. TLVs: chassis/port ID (MAC), port description,
  system name (net.hostname), system description (project + version),
  capabilities station-only, IPv4 management address.
- Docs: LLDP in the core Network section; step 2a ticked.
- Verified on an HP 2530-8G-PoE+ (show lldp info remote-device 2): all
  fields shown, management address 192.168.192.244.

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

components/aes67_net/aes67_net.c

@@ -10,6 +10,7 @@
 #include "esp_event.h"
 #include "esp_log.h"
 #include "esp_netif.h"
+#include "lldp.h"
 #include "mdns.h"
 
 static const char *TAG = "net";
@@ -58,6 +59,7 @@ static void ip_event(void *arg, esp_event_base_t base, int32_t id, void *data)
     const ip_event_got_ip_t *ev = data;
     ESP_LOGI(TAG, "got IP " IPSTR " mask " IPSTR " gw " IPSTR,
              IP2STR(&ev->ip_info.ip), IP2STR(&ev->ip_info.netmask), IP2STR(&ev->ip_info.gw));
+    lldp_changed();
 }
 
 // Static addressing needs ip + mask; gw/dns are optional (none on the AES67 side with VLAN split).
@@ -129,6 +131,7 @@ static void net_apply(const cJSON *g)
     if (mdns_hostname_set(host) == ESP_OK && mdns_instance_name_set(host) == ESP_OK) {
         ESP_LOGI(TAG, "mDNS: now %s.local", host);
     }
+    lldp_changed();
 }
 
 static void net_status(cJSON *st)
@@ -170,6 +173,7 @@ esp_err_t aes67_net_init(esp_eth_handle_t eth)
     ESP_ERROR_CHECK(esp_event_handler_register(IP_EVENT, IP_EVENT_ETH_GOT_IP, ip_event, NULL));
 
     mdns_setup();
+    ESP_ERROR_CHECK(lldp_start(eth, s_netif));
     status_register(net_status);
     return esp_eth_start(eth);
 }