feat(cc-digital-channel): add-uts-for-digital-channel

[akulakum]

COMPLETES #https://jira-eng-sjc12.cisco.com/jira/browse/CAI-7458

This pull request addresses

Adding comprehensive unit tests for the cc-digital-channels package to improve code coverage and test reliability.

by making the following changes

• Added unit tests for useDigitalChannelsInit and useDigitalChannelsData hooks covering initialization, error handling, and edge cases.
• Created dedicated DigitalChannelsComponent.test.tsx for presentational component tests (theme rendering, props validation).
• Added ErrorBoundary integration test for DigitalChannels component

Change Type

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Tooling change
• Internal code refactor

The following scenarios were tested

• The testing is done with the amplify link
  < ENUMERATE TESTS PERFORMED, WHETHER MANUAL OR AUTOMATED >

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• GAI was not used (or, no additional notation is required)
• Code was generated entirely by GAI
• GAI was used to create a draft that was subsequently customized or modified
• Coder created a draft manually that was non-substantively modified by GAI (e.g., refactoring was performed by GAI on manually written code)
• Tool used for AI assistance (GitHub Copilot / Other - specify)
  • Github Copilot
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• This PR is related to
  • Feature
  • Defect fix
  • Tech Debt
  • Automation

Checklist before merging

• I have not skipped any automated checks
• All existing and new tests passed
• I have updated the testing document
• I have tested the functionality with amplify link

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