[mdns] Restore USE_MDNS_EVENT_DRIVEN_POLLING guards around listener definitions

clang-tidy CI compiles with the raw esp8266-arduino-tidy env's flags — no
Python codegen, and it doesn't pick up the feature defines from defines.h in
the same way a real IDE does. USE_WIFI_IP_STATE_LISTENERS ends up undefined,
the derivation in mdns_component.h doesn't fire, and the class doesn't declare
start_polling_window_ / on_ip_state / the MDNS_POLL_* constants. Removing the
guards in the platform cpps made those definitions dangle.

Keep the listener-specific definitions under #ifdef USE_MDNS_EVENT_DRIVEN_POLLING.
The Python validator still enforces the runtime invariant (wifi or ethernet
must be present on ESP8266/RP2040), so production builds always fire through
the listener path; this is purely about what the tidy compiler sees.

esphome/components/mdns/mdns_esp8266.cpp

@@ -38,21 +38,26 @@ static void register_esp8266(MDNSComponent *, StaticVector<MDNSService, MDNS_SER
   }
 }
 
+#ifdef USE_MDNS_EVENT_DRIVEN_POLLING
 void MDNSComponent::start_polling_window_() {
   // uint32_t-ID set_interval/set_timeout already does atomic cancel-and-add.
   this->set_interval(MDNS_POLL_ID, MDNS_UPDATE_INTERVAL_MS, []() { MDNS.update(); });
   this->set_timeout(MDNS_POLL_STOP_ID, MDNS_POLL_WINDOW_MS, [this]() { this->cancel_interval(MDNS_POLL_ID); });
 }
+#endif
 
 void MDNSComponent::setup() {
   this->setup_buffers_and_register_(register_esp8266);
+#ifdef USE_MDNS_EVENT_DRIVEN_POLLING
   // LEAmDNS's own LwipIntf::statusChangeCB drives _restart() on netif changes; we just
   // arm the window around the initial probe/announce and each reconnect. Unconditional
   // here is safe: setup_priority::AFTER_CONNECTION guarantees the network is up.
   wifi::global_wifi_component->add_ip_state_listener(this);
   this->start_polling_window_();
+#endif
 }
 
+#ifdef USE_MDNS_EVENT_DRIVEN_POLLING
 void MDNSComponent::on_ip_state(const network::IPAddresses &ips, const network::IPAddress &,
                                 const network::IPAddress &) {
   // IP listener only fires on acquisition (not loss), so any notification is a fresh
@@ -61,6 +66,7 @@ void MDNSComponent::on_ip_state(const network::IPAddresses &ips, const network::
     this->start_polling_window_();
   }
 }
+#endif
 
 void MDNSComponent::on_shutdown() {
   MDNS.close();

esphome/components/mdns/mdns_rp2040.cpp

@@ -38,11 +38,13 @@ static void register_rp2040(MDNSComponent *, StaticVector<MDNSService, MDNS_SERV
   }
 }
 
+#ifdef USE_MDNS_EVENT_DRIVEN_POLLING
 void MDNSComponent::start_polling_window_() {
   // uint32_t-ID set_interval/set_timeout already does atomic cancel-and-add.
   this->set_interval(MDNS_POLL_ID, MDNS_UPDATE_INTERVAL_MS, []() { MDNS.update(); });
   this->set_timeout(MDNS_POLL_STOP_ID, MDNS_POLL_WINDOW_MS, [this]() { this->cancel_interval(MDNS_POLL_ID); });
 }
+#endif
 
 void MDNSComponent::setup() {
   // arduino-pico stubs out LwipIntf::stateUpCB (the netif status callback LEAmDNS uses
@@ -72,6 +74,7 @@ void MDNSComponent::setup() {
 #endif
 }
 
+#ifdef USE_MDNS_EVENT_DRIVEN_POLLING
 void MDNSComponent::on_ip_state(const network::IPAddresses &ips, const network::IPAddress &,
                                 const network::IPAddress &) {
   // Listener only fires on IP acquisition (not loss); every event is a fresh IP.
@@ -86,6 +89,7 @@ void MDNSComponent::on_ip_state(const network::IPAddresses &ips, const network::
   }
   this->start_polling_window_();
 }
+#endif
 
 void MDNSComponent::on_shutdown() {
   MDNS.close();