test: add clipboard and sort-order preference integration tests

[wheval]

Summary

• Add integration test for copy-to-clipboard button copying full unmasked wallet address #476 — CopyField clipboard test: renders CopyField, mocks navigator.clipboard.writeText, clicks the copy button, and asserts the full unmasked Stellar address (not a shortened form) is passed to the clipboard. Also verifies the copied-state aria-label update.

• Add integration test for localStorage preference helper persisting sort order across re-renders #478 — Sort order persistence: tests that setPreference/getPreference preserve a user's chosen sort order across simulated remounts, correctly reset to the default when localStorage is cleared, survive multiple toggles, and are isolated per storage key.

Test plan

• src/components/common/__tests__/CopyField.test.tsx — 3 tests
• src/utils/__tests__/preferences.sortOrder.test.ts — 4 tests

Closes #476
Closes #478