feat: add toast component unit tests

[Stanley-Owoh]

Add unit tests for toast component auto-dismiss and manual close

Summary

Added unit tests for showToast.success() confirming both the auto-dismiss timing and manual close behavior work correctly.

Changes

• New file: src/utils/__tests__/toast.util.test.tsx

Tests added

Test	Assertion
Toast visible immediately after render	getByText('Success message') is in the document
Toast still visible at 3999ms	After advanceTimersByTime(3999), toast remains in the DOM
Toast removed after auto-dismiss + remove delay	After advancing past 4000ms (dismiss) + 1000ms (REMOVE_DELAY), toast is removed from the DOM
Manual close removes toast before auto-dismiss	Calling toast.dismiss() removes the toast immediately without waiting for the timer

Notes

• Tests use vi.useFakeTimers() with a matchMedia mock required by react-hot-toast's <Toaster> component
• The <Toaster> from react-hot-toast is rendered directly in tests (not the app's <Toaster> from App.tsx) to isolate the toast utility
• react-hot-toast uses a two-phase removal: dismiss (sets visible: false) then a REMOVE_DELAY of 1000ms before unmounting from the DOM

Closes #628

[drips-wave]

@Stanley-Owoh Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits