fix(esp8266): disable WiFi modem-sleep on station connect

Set WiFi.setSleepMode(WIFI_NONE_SLEEP) in the GOT_IP handler, after
mAp.disable() completes the AP→STA mode transition. Placement after the
mode change ensures the sleep setting is not reset, and re-applies on
every reconnect.

Without this, ESP8266 defaults to modem-sleep. At weak RSSI the STA
misses DTIM beacons, causing outbound TCP (MQTT) to wedge while the
async web server remains reachable — a "zombie" state recoverable only
by inbound LAN traffic or reboot.

src/network/AhoyWifiEsp8266.h

@@ -91,6 +91,7 @@ class AhoyWifi : public AhoyNetwork {
                 case NetworkState::GOT_IP:
                     if(!mConnected) {
                         mAp.disable();
+                        WiFi.setSleepMode(WIFI_NONE_SLEEP);
                         mConnected = true;
                         ah::welcome(WiFi.localIP().toString(), F("Station"));
                         MDNS.begin(mConfig->sys.deviceName);