fix(config): consolidate to single vitest.config.ts and remove vitest.config.mts (#523)

[lmduy2612]

Summary

Closes #523.

Consolidates the test configuration into a single canonical vitest.config.ts file and removes the duplicate vitest.config.mts and its orphaned setup file src/test/setup.ts.

Changes Made

• Removed redundant vitest.config.mts from project root.
• Removed unused src/test/setup.ts which was only referenced by vitest.config.mts.
• Standardized both local and CI test execution on the primary vitest.config.ts containing the full test suite configuration, jsdom environment, aliases, and coverage setup.

Acceptance Criteria

• Consolidate to a single vitest config file (vitest.config.ts)
• CI and local test runs use the same config
• Remove the unused config file (vitest.config.mts)

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