Fix roborock off peak electricity timer

[allenporter]

Proposed change

Fix roborock off peak electricity timer time entities.

The existing code was calling the wrong API methods, which is defined here: https://github.com/Python-roborock/python-roborock/blob/main/roborock/devices/traits/v1/valley_electricity_timer.py -- this adds tests for the entities, sharing a fixture with the existing do not disturb time entities.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes Roborock on/off peak time chamge not work after HA Core update #158245
• This PR is related to issue:
• Link to documentation pull request:
• Link to developer documentation pull request:
• Link to frontend pull request:

Checklist

• I understand the code I am submitting and can explain how it works.
• The code change is tested and works locally.
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• There is no commented out code in this PR.
• I have followed the development checklist
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• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.
• Any generated code has been carefully reviewed for correctness and compliance with project standards.

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[home-assistant]

Hey there @Lash-L, mind taking a look at this pull request as it has been labeled with an integration (roborock) you are listed as a code owner for? Thanks!

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[Copilot]

Pull request overview

This PR fixes a bug in the Roborock integration's off-peak electricity timer time entities by correcting the API method calls to match the upstream library's interface.

• Changes the off-peak timer entities to use the correct set_timer method instead of the incorrect update_value method
• Adds comprehensive test coverage for both off-peak timer entities (start and end times)
• Updates test fixtures to properly mock the valley electricity timer trait

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
homeassistant/components/roborock/time.py	Fixed off-peak timer entities to call trait.set_timer() with ValleyElectricityTimer dataclass instead of incorrect update_value() method
tests/components/roborock/test_time.py	Added test cases for off-peak start and end time entities, refactored test structure to use callable parameter for flexibility
tests/components/roborock/conftest.py	Added make_valley_electric_timer fixture function to properly mock the valley electricity timer trait with set_timer method
tests/components/roborock/mock_data.py	Added VALLEY_ELECTRICITY_TIMER mock data constant for test fixtures