Add comprehensive Jest unit tests for cryptoformat module

[devin-ai-integration]

Add comprehensive Jest unit tests for cryptoformat module (rebased for Jest v30)

Summary

This PR adds 317 lines of comprehensive Jest unit tests to src/test.js, expanding test coverage from basic functionality to extensive edge cases, error conditions, and boundary testing for all exported functions (formatCurrency, isCrypto, clearCache) and internal helper functions.

The PR has been rebased from master to include the Jest v30.1.1 upgrade (previously v24.9.0). All 72 tests pass with the new Jest version.

Key test additions:

• Internal helper function testing: isBTCETH, IntlNumberFormatSupported, fallback behavior
• Edge case coverage: Invalid inputs (null, undefined, NaN, Infinity), boundary values, locale-specific cases
• Error handling: Unsupported currencies, invalid locales, global state corruption scenarios
• Caching mechanism: Verification that clearCache() works and formatters are reused appropriately
• Symbol overrides: Currency symbol customization functionality
• Complex parameters: Decimal places, significant figures, trailing zeroes handling
• Fallback scenarios: Behavior when Intl.NumberFormat is unavailable

Review & Testing Checklist for Human

• Verify test expectations are correct - Some test expectations were adjusted during development, manually verify key behaviors match actual library output
• Test Jest v30 compatibility - Run tests in your local environment and CI to ensure the major Jest upgrade doesn't introduce issues
• Manual spot-check edge cases - Try some of the edge cases manually (very small numbers, invalid inputs, etc.) to verify test expectations
• Review global state handling - Tests modify global.Intl - ensure this doesn't cause issues in your test environment

Notes

• All 72 tests pass locally with Jest v30.1.1
• No breaking changes were required for Jest v30 compatibility
• Tests use existing babel configuration and Jest defaults (no jest.config file needed)
• Link to Devin run: https://app.devin.ai/sessions/f64ceefe350e4a42bf304bfacf32c3f7
• Originally requested by: cedric@coingecko.com, rebase requested by: jason.julian

[devin-ai-integration]

Original prompt from cedric@coingecko.com

In the cryptoformat repo, look into the file https://github.com/coingecko/cryptoformat/blob/master/src/index.js. Set up unit tests for this module to test all happy path and edge cases for each function using Jest

[devin-ai-integration]

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[jasonjul]

Approved, Devin's work