refactor: update ecommerce module to TS

[jaissica12]

Background

• Migrate remaining JavaScript modules to TypeScript for improved type safety and developer experience across the SDK codebase.

What Has Changed

• Converted src/ecommerce.js to src/ecommerce.ts with full type annotations on all methods and parameters
• Converted test/src/tests-eCommerce.js to test/src/tests-eCommerce.ts with necessary type casts for intentional type-mismatch tests that validate error handling

Screenshots/Video

• N/A (no UI changes)

Checklist

• I have performed a self-review of my own code.
• I have made corresponding changes to the documentation.
• I have added tests that prove my fix is effective or that my feature works.
• I have tested this locally.

Additional Notes

• No logic changes — this is a pure TypeScript conversion with type annotations added
• Lint, build, and all 556 Jest tests pass

Reference Issue (For employees only. Ignore if you are an outside contributor)

• Closes https://go/j/SDKE-1108

[sonarqubecloud]

Quality Gate failed

Failed conditions
10.3% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud