Add EEPROM EUI-48 device identity across firmware and API.

Read the factory 24AA025E48 serial after ADAU I2C boot, derive SoftAP SSID, BT name, STA hostname, and expose serialNumber on GET /api/health with graceful fallbacks.

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/components/net/src/StaClient.cpp

@@ -20,12 +20,15 @@
 
 #include "esp_event.h"
 #include "esp_log.h"
+#include "esp_netif.h"
 #include "esp_wifi.h"
+#include "mdns.h"
 #include "freertos/FreeRTOS.h"
 #include "freertos/event_groups.h"
 
 #include <algorithm>
 #include <cstring>
+#include <string>
 
 namespace net {
 
@@ -104,12 +107,17 @@ StaClient& StaClient::operator=(StaClient&& other) noexcept
 }
 
 std::expected<void, NetError>
-StaClient::connect(const core::WifiCredentials& creds)
+StaClient::connect(const core::WifiCredentials& creds, std::string_view hostname)
 {
     if (connected_) {
         return {};
     }
 
+    std::string hostLabel;
+    if (!hostname.empty()) {
+        hostLabel.assign(hostname.begin(), hostname.end());
+    }
+
     s_wifiEventGroup = xEventGroupCreate();
     if (s_wifiEventGroup == nullptr) {
         return std::unexpected(NetError::StaConnectFailed);
@@ -132,6 +140,13 @@ StaClient::connect(const core::WifiCredentials& creds)
         return std::unexpected(NetError::WifiConfigFailed);
     }
 
+    if (!hostLabel.empty()) {
+        esp_netif_t* netif = esp_netif_get_handle_from_ifkey("WIFI_STA_DEF");
+        if (netif != nullptr) {
+            esp_netif_set_hostname(netif, hostLabel.c_str());
+        }
+    }
+
     wifi_config_t wifiCfg = {};
     const std::string_view ssid = creds.ssid().value();
     const std::size_t ssidCopy =
@@ -167,6 +182,11 @@ StaClient::connect(const core::WifiCredentials& creds)
 
     if ((bits & kConnectedBit) != 0) {
         connected_ = true;
+        if (!hostLabel.empty()) {
+            if (mdns_init() == ESP_OK) {
+                mdns_hostname_set(hostLabel.c_str());
+            }
+        }
         ESP_LOGI(kTag, "connected to %.*s",
                  static_cast<int>(ssid.size()), ssid.data());
         return {};