[GOOD FIRST ISSUE] Add unit tests for formatLocaleDate and formatLocaleTime fallback behavior

[utksh1]

Summary

frontend/src/utils/date.ts has several date formatting helpers. Add focused tests for invalid, empty, and Date object inputs for formatLocaleDate and formatLocaleTime.

Scope

• Update or add tests near frontend/testing/unit/utils/date.test.ts.
• Use fixed dates and, if needed, mocked timezone/localStorage.
• Avoid dynamic current-date assertions.

Acceptance Criteria

• Invalid/empty inputs return the expected fallback string.
• Date object inputs format consistently.
• Tests are deterministic across timezones.

[SaumyaT-21]

Hello @utksh1 ! I’m a GSSoC '26 contributor and I'd like to work on this! I understand the requirements for deterministic testing and handling edge cases for this behaviour. Could you please assign this to me?