TempMQTT U1.0 - Project UNION

Based on:
- NodeMCU TempMQTT WebConfig v1.9
- UNION Consolidation v0.1

Main architectural split:
- UNION: language, shared web layout, WiFi, MQTT connection, System, Firmware, Info framework
- Project: DHT sensor, OLED, LED control and project-specific MQTT topics

Board:
NodeMCU 1.0 (ESP-12E Module)

Libraries:
ESP8266 core, DHTesp, PubSubClient, ArduinoJson, Adafruit_GFX, Adafruit_SSD1306

Important:
This is the first UNION migration of an ESP8266/NodeMCU project. The UNION user interface follows the ESP32 reference projects, while low-level WiFi, storage and firmware code is adapted to ESP8266.
