Add function to check internal network availability

[stremskijdmitro]

Added a new function is_internal_network_available to determine if the Home Assistant instance has access to the internal network. This function attempts to connect to a specified router IP address and port to verify network availability. Useful for enabling or disabling features based on internal network connectivity.

Breaking change

Proposed change

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 #
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Checklist

• The code change is tested and works locally.
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• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

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

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  Updated and included derived files by running: python3 -m script.hassfest.
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[home-assistant]

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[home-assistant]

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[frenck]

What is using this?

[frenck]

This makes an assumption the router has a web interface (hint: mine has not...)