Add P1/P2 Mini Multi-Split Support & Update Documentation

[chenzhuo1005]

This PR adds initial support for Daikin P1/P2 mini multi-split indoor units (tested on FDMQ12WVJU9 and FDMQ24WVJU9), updates the README, and makes a handful of related improvements:

• New DaikinSplitUnit fields for P1/P2 split systems:

  • Parses set_point_heat / set_point_cool fallback when API returns 65535
  • Adds operating_time (minutes) and equipment_status enum

• Extended sensor entities to expose:

  • P1/P2 suction, discharge, coil, heat-exchanger, and gas-pipe temperatures
  • EEV pulses, energized time, fan runtime, fan speed & tap, flap swing

• Fan speed control

  • Defined a new DaikinThermostatFanSpeed enum

  • Enhanced set_thermostat_fan_speed() to handle P1/P2 mini multi-split mapping:

    • AUTO=0, LOW=1, MEDIUM=3, HIGH=5

  • Note: fan speed commands on these models are currently non-functional—investigation ongoing.

• Documentation:

  • README updated to note mini multi-split support, tested models, and known fan-speed limitation
  • Added badge and “Supported Equipment” entries for FDMQ12WVJU9 & FDMQ24WVJU9

Testing:

• Verified entity discovery and state reporting in Home Assistant for both FDMQ12WVJU9 and FDMQ24WVJU9
• Confirmed temperature, humidity, airflow, demand, and P1/P2 stats populate correctly
• Confirmed the thermostat UI can control power (on/off), system mode (cool/heat), and set temperature

Next Steps:

• Troubleshoot and restore fan-speed control support on mini multi-split units
• Add integration tests for new equipment types