Add tests for TopMoversCard

[christabel888]

Context: Test coverage for #42-#44.

Where:

• src/components/__tests__/TopMoversCard.test.tsx

What to do:

• Cover rendering with data, loading, empty, and the share action.

Suggested approach:

1. Cover rendering with data, loading, empty, and the share action from Add native share-sheet (Twitter/X) action on TopMoversCard #44.

Watch out for:

• None beyond standard test hygiene.

Definition of done:

• Test file exists and covers all states