Migrate ESLint configuration to v9 flat config format

[Copilot]

This PR migrates the ESLint configuration from the legacy .eslintrc.js format to the new flat configuration format required by ESLint v9.33.0.

Changes Made

ESLint Configuration Migration

• Removed .eslintrc.js (legacy format)
• Added eslint.config.js with ESLint v9 flat config format
• Migrated all custom rules from the original configuration:
  • Semi-colon enforcement
  • Single quote preference
  • Comma-dangle disabled
  • Custom spacing and formatting rules
• Added proper Node.js globals configuration
• Configured separate rules for test files with Mocha globals

Dependency Updates

• Updated ESLint from 4.9.0 to ^9.33.0
• Removed obsolete ESLint plugins that are no longer needed with the new configuration format

Workflow Updates

• Updated publish-artificats.yml workflow to use Node.js 20.x (from 10.15.3) for ESLint v9 compatibility
• Updated GitHub Actions versions for better security and compatibility

Validation

• All existing tests continue to pass
• Code coverage maintained at 96%+
• Linting works correctly with the new configuration
• No changes to actual code formatting or linting behavior

The migration resolves the error encountered when dependabot attempts to upgrade ESLint:

ESLint: 9.33.0
ESLint couldn't find an eslint.config.(js|mjs|cjs) file.

Fixes #25.

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[github-actions]

File	Coverage	Lines	Branches
All files	96%	96%	96%	✅

Minimum allowed coverage is 90%

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