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'

Tactility/Source/service/webserver/WebServerService.cpp

@@ -46,6 +46,8 @@
 #include <esp_system.h>
 #include <esp_vfs_fat.h>
 #include <esp_wifi.h>
+#include <mdns.h>
+#include <esp_mac.h>
 #include <freertos/FreeRTOS.h>
 #include <freertos/task.h>
 #include <iomanip>
@@ -392,6 +394,27 @@ bool WebServerService::startApMode() {
     }
 
     LOG_I(TAG, "WiFi AP started - SSID: '%s', Channel: %u, IP: 192.168.4.1", settings.apSsid.c_str(), (unsigned)settings.apChannel);
+
+    // mDNS for AP mode too - kidsOS-XXXX.local
+    {
+        uint8_t mac[6];
+        char hostname[32];
+        if (esp_wifi_get_mac(WIFI_IF_AP, mac) == ESP_OK) {
+            snprintf(hostname, sizeof(hostname), "kidsOS-%02X%02X", mac[4], mac[5]);
+        } else {
+            strncpy(hostname, "kidsOS", sizeof(hostname));
+        }
+        esp_netif_set_hostname(apNetif, hostname);
+        esp_err_t mdns_err = mdns_init();
+        if (mdns_err == ESP_OK) {
+            LOG_I(TAG, "mDNS AP 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);
+        }
+    }
+
     return true;
 }