feat(mdns): restore mDNS + hostname kidsOS-XXXX

- Add espressif/mdns 1.3.2 to idf_component.yml + CMake
- STA path (esp32_wifi.cpp): set DHCP hostname kidsOS-XXXY from MAC,
  mdns_init, hostname, instance, _http:80 + _tactility:6666 services
- AP path (WebServerService.cpp): same hostname + mDNS for AP mode
- Log: mDNS AP/STA initialized hostname 'kidsOS-91ED.local'
- Previous implementation from 300ddb3a lost in driver arch migration
  f9453d89 (#562 #574)

Tested: RLCD 0x2d5470 FLASH_EXIT:0, log shows
  'mDNS AP initialized, hostname kidsOS-91ED.local'

Platforms/platform-esp32/source/drivers/esp32_wifi.cpp

@@ -5,9 +5,11 @@
 #if defined(CONFIG_SOC_WIFI_SUPPORTED) || defined(CONFIG_SLAVE_SOC_WIFI_SUPPORTED)
 
 #include <esp_event.h>
+#include <esp_mac.h>
 #include <esp_netif.h>
 #include <esp_wifi.h>
 #include <esp_wifi_default.h>
+#include <mdns.h>
 
 #include <tactility/concurrent/mutex.h>
 #include <tactility/device.h>
@@ -151,6 +153,31 @@ error_t bring_up_wifi(Esp32WifiCtx* ctx) {
         return ERROR_RESOURCE;
     }
 
+    // mDNS + hostname: kidsOS-XXXX from MAC, for Bonjour discovery
+    {
+        uint8_t mac[6];
+        char hostname[32];
+        if (esp_wifi_get_mac(WIFI_IF_STA, mac) == ESP_OK) {
+            snprintf(hostname, sizeof(hostname), "kidsOS-%02X%02X", mac[4], mac[5]);
+        } else {
+            strncpy(hostname, "kidsOS", sizeof(hostname));
+        }
+        LOG_I(TAG, "Setting DHCP hostname to '%s'", hostname);
+        esp_netif_set_hostname(ctx->netif, hostname);
+
+        esp_err_t mdns_err = mdns_init();
+        if (mdns_err == ESP_OK) {
+            LOG_I(TAG, "mDNS initialized, hostname '%s.local'", hostname);
+            mdns_hostname_set(hostname);
+            mdns_instance_name_set("kidsOS Tactility Device");
+            mdns_service_add(NULL, "_http", "_tcp", 80, NULL, 0);
+            mdns_service_add(NULL, "_tactility", "_tcp", 6666, NULL, 0);
+        } else {
+            LOG_W(TAG, "mDNS init failed: %s", esp_err_to_name(mdns_err));
+        }
+    }
+
+
     // Warning: this is the memory-intensive operation. It uses over 100kB of
     // RAM with default settings.
     wifi_init_config_t init_config = WIFI_INIT_CONFIG_DEFAULT();