Fix Xiaomi Smart Doorbell 4 Pro dual-camera events

[wmgylc]

Summary

• expose both cloud camera channels for midr.cateye.sd400
• keep channel 10 on the existing downward-facing doorbell camera entity
• add channel 0 as a separate main-camera entity
• reuse the integration's existing snapshot and MJPEG proxy behavior

Root cause

The Xiaomi Smart Doorbell 4 Pro returns paired entries in thirdPartPlayUnits: channel 0 is the main camera and channel 10 is the downward-facing camera. The integration previously consumed only the first event, which is why only the downward-facing view was exposed.

Implementation

The event-list helper can now optionally retain the latest event for each channel while preserving its existing return value and default behavior. The model-specific camera path consumes that channel map, keeps channel 10 on the current entity, and creates one BaseSubEntity camera for channel 0.

The change is scoped to midr.cateye.sd400; all other camera models continue using the existing first-event behavior. Event dictionaries are copied before normalization so the cloud response is not mutated.

中文说明

本 PR 修复米家智能可视门铃 4 Pro（midr.cateye.sd400）在 Home Assistant 中只能看到下视摄像头的问题。该设备的云端事件会同时返回两个通道：0 为主摄像头，10 为下视摄像头；修改后会分别显示为两个摄像头实体，并已在真实设备上验证快照及 MJPEG 动态画面。

Validation

• python -m pytest -q tests/test_camera_channels.py — 1 passed
• Python compilation check
• git diff --check
• Home Assistant restart with both camera entities available
• Both snapshot endpoints return 200 image/jpeg
• Both camera proxy streams return 200 multipart/x-mixed-replace

Tested on hardware with:

• Home Assistant 2025.6.3
• Xiaomi Miot Auto 1.1.4
• midr.cateye.sd400

Fixes #2675

[gemini-code-assist]

Caution

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