Adds env-scoped hooks for the alerts inbox:
- useAlerts (30s poll, background-paused, filter-aware)
- useAlert, useUnreadCount (30s poll)
- useAckAlert, useMarkAlertRead, useBulkReadAlerts (mutations that
invalidate the alerts query key tree + unread-count)
Test file uses .tsx because the QueryClientProvider wrapper relies on
JSX; vitest picks up both .ts and .tsx via the configured include glob.
Client mock targets the actual export name (`api` in ../client) rather
than the `apiClient` alias that alertMeta re-exports.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
