Enhance documentation and expand test coverage

[DenisPalnitsky]

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Summary

This PR improves the project documentation and significantly expands test coverage for the JUnit reader functionality.

• Added comprehensive setup and testing instructions to the backend README
• Added 14 new test cases to JUnitReaderTests covering edge cases and various XML parsing scenarios
• Included dotnet-install.sh script for streamlined .NET SDK installation
• Updated .gitignore to exclude Claude Code configuration directory

Changes

Documentation

• README.md: Added detailed sections for:
  • Prerequisites (.NET 6.0 SDK)
  • Setup instructions (restore, build, run)
  • Testing instructions with multiple options (unit tests, integration tests, coverage)

Test Coverage

• JUnitReaderTests.cs: Added 14 new test cases:
  • Visitor pattern functionality
  • Test run status handling (passed/failed)
  • Test run properties validation
  • Error and system error handling
  • Skipped test handling
  • System output handling
  • Edge cases (missing className, invalid time values, scientific notation)
  • Multiple test suites handling
  • Case-insensitive XML element parsing

Infrastructure

• dotnet-install.sh: Added official .NET installation script for easier local development setup
• .gitignore: Added .claude directory to prevent committing IDE configuration

Test plan

• Verify all existing tests still pass
• Verify new test cases pass
• Verify README instructions are accurate by following setup steps on a clean environment
• Confirm .gitignore properly excludes .claude directory

🤖 Generated with Claude Code
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