docs: реконструкция LAN-протокола FGLair, анализ legacy, планы fglair-core/HA/ESPHome

- PROTOCOL.md: полная спецификация (KDF, envelope/CBC-цепочка, local_reg,
  key exchange, commands.json 206/200, datapoint push, тайминги, таблицы
  свойств шаблонов A/B/F, облачный provisioning). Факты из APK помечены
  [APK], проверенные живыми экспериментами на AP-WC1E — [ПРОВЕРЕНО НА
  ПРИБОРЕ]: mDNS только :10276; лимит 2 LAN-сессии (3-я -> 503);
  принудительный re-key при возрасте сессии >= ~44с (единственный механизм
  самолечения десинхрона — 400/401 модуль игнорирует); записи не
  эхируются; delete_session освобождает слот.
- LEGACY_ANALYSIS.md: причины рассинхрона (keep-alive 1200с вместо 10-15с
  + seq_no-фильтр) и перегрузки модуля; требования к новой реализации.
- PLAN_CORE_LIBRARY.md: план C++20-библиотеки fglair-core (Linux + ESP-IDF),
  ключ lanip_key считается статичным, ротация — только ошибка + ручной
  перепровижининг.
- PLAN_HOME_ASSISTANT.md: pyfglair (cffi wheel) + custom component,
  облачный provisioning только в config flow, ключ виден в диагностике
  для копирования в ESPHome.
- PLAN_ESPHOME.md: external component, только ESP-IDF framework.
- tools/probe_reference.py: эталонный клиент протокола (проверен на
  приборе end-to-end); tools/probe_mdns.py — mDNS-проба.
- legacy/: снимок скрипта (апстрим gyro-labs/AirCon, вложенный клон не
  версионируется); apk/*.apk исключены из версионирования.

legacy/mqtt_client.py

@@ -0,0 +1,92 @@
+from dataclasses import fields
+import enum
+import logging
+import paho.mqtt.client as mqtt
+
+from .aircon import Device
+from .properties import AcWorkMode, FglOperationMode
+
+
+class MqttClient(mqtt.Client):
+
+  def __init__(self, client_id: str, mqtt_topics: dict, devices: [Device]):
+    super().__init__(client_id=client_id, clean_session=True)
+    self._mqtt_topics = mqtt_topics
+    self._devices = devices
+
+    self.on_connect = self.mqtt_on_connect
+    self.on_message = self.mqtt_on_message
+
+  def mqtt_on_connect(self, client: mqtt.Client, userdata, flags, rc):
+    for device in self._devices:
+      topics_fmt = [(self._mqtt_topics['sub'].format(device.mac_address, data_field.name), 0)
+                        for data_field in fields(device.get_all_properties())]
+      logging.debug(f"Subscribing to topics{topics_fmt} for device {device}")
+      client.subscribe(topics_fmt)
+    # Subscribe to subscription updates.
+    client.subscribe('$SYS/broker/log/M/subscribe/#')
+
+    # Publish current status of all properties for available devices.
+    for device in self._devices:
+      if device.available:
+        for prop_name in fields(device.get_all_properties()):
+          self.mqtt_publish_update(device.mac_address,
+                                   prop_name,
+                                   device.get_property(prop_name),
+                                   retain=False)
+
+  def mqtt_on_message(self, client: mqtt.Client, userdata, message: mqtt.MQTTMessage):
+    logging.info('MQTT message Topic: {}, Payload {}'.format(message.topic, message.payload))
+    if message.topic.startswith('$SYS/broker/log/M/subscribe'):
+      return self.mqtt_on_subscribe(message.payload)
+    mac_address = message.topic.rsplit('/', 3)[1]
+    prop_name = message.topic.rsplit('/', 3)[2]
+    payload = message.payload.decode('utf-8')
+    if prop_name == 't_work_mode':
+      if payload == 'fan_only':
+        payload = 'FAN'
+
+    for device in self._devices:
+      if device.mac_address != mac_address:
+        continue
+      chosen_device = device
+
+    try:
+      chosen_device.queue_command(prop_name, payload.upper())
+    except Exception:
+      logging.exception('Failed to parse value {} for property {}'.format(
+          payload.upper(), prop_name))
+
+  def mqtt_on_subscribe(self, payload: bytes):
+    # The last segment in the space delimited string is the topic.
+    topic = payload.decode('utf-8').rsplit(' ', 1)[-1]
+    if topic not in self._mqtt_topics['pub']:
+      return
+    mac_address = topic.rsplit('/', 3)[1]
+    prop_name = topic.rsplit('/', 3)[2]
+
+    for device in self._devices:
+      if device.mac_address != mac_address:
+        continue
+      chosen_device = device
+
+    self.mqtt_publish_update(chosen_device.mac_address,
+                             prop_name,
+                             chosen_device.get_property(prop_name),
+                             retain=False)
+
+  def mqtt_publish_update(self,
+                          mac_address: str,
+                          property_name: str,
+                          value,
+                          retain: bool = False) -> None:
+    if isinstance(value, enum.Enum):
+      payload = 'fan_only' if (value is AcWorkMode.FAN or
+                               value is FglOperationMode.FAN_ONLY) else value.name.lower()
+    else:
+      payload = str(value)
+    topic = self._mqtt_topics['pub'].format(mac_address, property_name)
+    logging.info('Sending MQTT update Topic: {}, Payload {}'.format(topic, payload))
+    self.publish(topic,
+                 payload=payload.encode('utf-8'),
+                 retain=retain)