Import ESP_UniClock (upstream 1189810)

Vendored from https://github.com/gpeter62/ESP_UniClock: the sketch
source, the web UI and the libraries the ESP8266 build needs, unpacked
from the bundled zips. Adds a PlatformIO project for the ESP-12. The
source is unchanged; local changes follow as separate commits.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

firmware/uniclock/lib/arduino-home-assistant-main/examples/mqtt-advanced/mqtt-advanced.ino

@@ -0,0 +1,56 @@
+#include <Ethernet.h>
+#include <ArduinoHA.h>
+
+#define BROKER_ADDR         IPAddress(192,168,0,17)
+
+byte mac[] = {0x00, 0x10, 0xFA, 0x6E, 0x38, 0x4A};
+
+EthernetClient client;
+HADevice device(mac, sizeof(mac));
+HAMqtt mqtt(client, device);
+
+void onMqttMessage(const char* topic, const uint8_t* payload, uint16_t length) {
+    // This callback is called when message from MQTT broker is received.
+    // Please note that you should always verify if the message's topic is the one you expect.
+    // For example: if (memcmp(topic, "myCustomTopic") == 0) { ... }
+
+    Serial.print("New message on topic: ");
+    Serial.println(topic);
+    Serial.print("Data: ");
+    Serial.println((const char*)payload);
+
+    mqtt.publish("myPublishTopic", "hello");
+}
+
+void onMqttConnected() {
+    Serial.println("Connected to the broker!");
+
+    // You can subscribe to custom topic if you need
+    mqtt.subscribe("myCustomTopic");
+}
+
+void onMqttConnectionFailed() {
+    Serial.println("Failed to connect to the broker!");
+}
+
+void setup() {
+    Serial.begin(9600);
+    Ethernet.begin(mac);
+
+    mqtt.onMessage(onMqttMessage);
+    mqtt.onConnected(onMqttConnected);
+    mqtt.onConnectionFailed(onMqttConnectionFailed);
+
+    // If you use custom discovery prefix you can change it as following:
+    // mqtt.setDiscoveryPrefix("customPrefix");
+
+    // If you want to change prefix only for non-discovery prefix:
+    // mqtt.setDataPrefix("data");
+
+    mqtt.begin(BROKER_ADDR);
+}
+
+void loop() {
+    Ethernet.maintain();
+    mqtt.loop();
+}