Remove dead getPreferences / updatePreferences API client methods

Part of #1707. Found in the review of #1689.

## Problem

`getPreferences` and `updatePreferences` in `packages/shared/services/api-client/api-client.ts` (around line 67) are dead after the Preferences page deletion: the deleted page was their sole caller. A repo-wide grep (excluding tests and `node_modules`) shows zero callers of `apiClient.getPreferences` / `apiClient.updatePreferences`. The PR says the backend endpoints are being kept only for a future first setting, so a client surface that invites a consumer is misleading.

Likewise `WorkflowRunResponse.status` (`types.ts:135`) has no production reader now that the runs page is gone.

## Suggested fix

Remove the two client methods. Keep `UserPreferences`, since it types `UserMeResponse.preferences`. Optionally drop `status` from the TS type or annotate it as unused.

Start in packages/shared/services/api-client/api-client.ts around line 67 and inspect types.ts around line 135. Confirm with a repo-wide grep excluding tests and node_modules that the two preference methods have no callers, then check that UserPreferences is still used by UserMeResponse.preferences. Done means the dead methods are removed and the unused WorkflowRunResponse.status is either removed or clearly annotated.

Written by the indexing model from the issue text.