Add sensor platform to eq3btsmart

[EuleMitKeule]

Breaking change

Proposed change

This PR adds the sensor platform to the eq3btsmart integration. The new entities allow the user to observe the valve open percentage and the away until date of the thermostat.

Needs #130429 to get merged first.

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 #
• This PR is related to issue:
• Link to documentation pull request: Add sensor platform to eq3btsmart home-assistant.io#35723

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• I have followed the perfect PR recommendations
• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.

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• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.

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[home-assistant]

Hey there @dbuezas, mind taking a look at this pull request as it has been labeled with an integration (eq3btsmart) you are listed as a code owner for? Thanks!

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[home-assistant]

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