Handle concurrent device discovery and incomplete stream info

[diogormendes]

Summary

• coalesce concurrent device-list requests behind a shared lock while preserving the existing cache
• add an explicit force-refresh path for periodic device parameter updates
• accept stream-info responses that omit iot-device::iot-power when the camera is online
• avoid including raw API responses in exceptions, preventing tokens and device details from leaking into logs
• add regression coverage for stream responses without the power property

Validation

• python3.14 -m compileall -q src tests
• git diff --check
• regression test added in tests/test_camera_service.py

pytest could not be run in the local environment because the test dependencies are not installed and uv failed while creating its environment due to a macOS runtime issue.

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