Add Midea C3 heat pump (0xC3) support with SmartHomeCloud relay

[xelhark]

Summary

• Add DeviceType.HEAT_PUMP = 0xC3 to const.py
• Add HeatPump device class (device/C3/) with zone1/zone2, run modes (HEAT/COOL/AUTO/DHW), and full query/control command parsing
• Add SmartHomeCloud class with cloud relay support (appliance_transparent_send) — C3 devices use cloud relay because LAN V3 auth returns error 3004
• Route commands through cloud relay in base_device._send_command when a cloud instance is set (set_cloud())
• Add Device.construct() support for DeviceType.HEAT_PUMP
• Add Discover.probe_device_info(host) for ID-less discovery (sends UDP probe, returns device info without authenticating — needed since C3 uses SmartHomeCloud not NetHomePlusCloud)
• Stable pushToken (derived from account hash) to avoid "new device" push notifications on re-login
• Silent auto-re-login in appliance_transparent_send on token expiry (codes 3105/3106/3301/3001)

Notes

• C3 devices respond to UDP discovery but require SmartHomeCloud credentials (MSmartHome account), not NetHomePlusCloud
• QueryUnitParametersCommand returns error 3176 ("async reply") via cloud relay — outdoor temperature and power sensors are currently unavailable via this path
• Java-style signed bytes in relay CSV decoded correctly with & 0xFF

Test plan

• Tested against a real Midea C3 device (device_id=42880953506840) via cloud relay
• device.refresh() returns correct zone power state, target temperature, and run mode
• device.apply() sends control commands successfully via relay
• UDP probe_device_info() correctly extracts device ID without authentication
• Token expiry handled transparently with silent re-login

🤖 Generated with Claude Code

[mill1000]

Thanks for the PR. I'll appreciate the contribution.

I am interested in supporting additional climate device types, but I do not want to integrate additional cloud connectivity. The project is supposed to be for local control to which adding a cloud relay is antithetical.

So it is unlikely I will merge this PR as is.

A possible alternative, the cloud relay could be removed and stood up as a dedicated service that bridges between msmart-ng and your device. As far as msmart-ng would know, its just another device. The relay could even respond to discovery packets making the integration into HA pretty seamless. By using the "V2" packet format any need for key & token between msmart-ng and the relay is eliminated too.

flowchart LR
  A[msmart-ng] <-- UDP --> B
  B[cloud-relay] <-->
  C[Cloud]@{ shape: cloud }
  C <--> D[Device]

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Happy to discuss.