release: v0.5.6 – full multi-device support, correct scaling & precision

• Restore and unify support for 4Pro, WeatherDisplay, AQM2 and AQM3
• Fix all scaling rules according to firmware (x10 → /10)
• Display CO2 as integer ppm (no decimals)
• Apply consistent display precision (2 decimals for scaled values)
• Correct TID meaning (device / receiver type)
• Interpret AQM2 AVG_M as AQ_AVGMODE with human-readable state
• Keep AQI values raw as provided by firmware
• Update README with full device documentation