Fix/anchor detail loading flash

[zinodict121]

Fix AnchorDetail loading flash on deactivate

Fixes #277

What changed and why

Updated AnchorDetail to use await refresh() instead of reload() from useAsync after successfully deactivating an anchor.

Previously, calling reload() forced the UI back into a bare loading state, replacing the entire anchor detail card with a spinner and causing a visible layout flash. By using refresh() instead, the anchor data now re-fetches silently in the background, keeping the existing anchor data on screen. This matches the smoother UX consistency established in SettlementDetail's run() function.

Files touched

• src/components/AnchorDetail.tsx: Replaced reload() with refresh() and added inline documentation explaining the UX reasoning.
• src/components/AnchorDetail.test.tsx: Added new tests to cover the deactivation happy path and error handling.

Testing

• Added "deactivates an anchor without flashing a loading spinner": Verifies the happy path of the deactivation flow. It mocks a delayed fetch to assert that during the re-fetch process, the existing anchor data stays visible in the DOM (no "Loading anchor..." text appears) and that the status updates seamlessly to "Inactive" when the fetch resolves.
• Added "handles deactivation error gracefully": Verifies that if the deregisterAnchor API call rejects, the component correctly catches the error and finishes cleanly.
• useAsync was not modified. Its existing contract and return types already supported destructing and awaiting refresh().

All 7 tests in AnchorDetail.test.tsx are passing, and test coverage for AnchorDetail.tsx is at 100% across statements, lines, and branches.

Screenshots / Screen Recordings

(Add any relevant screenshots demonstrating the smooth transition here before submitting)