SearchUsers pagination loop has no page/row ceiling

## Problem

`lfx.Client.SearchUsers` (`lfx/client.go`) now paginates to exhaustion (fixed in #161 / commit `d453defd`), looping on `offset` until it sees a short page or `offset >= Metadata.TotalSize`. That's correct for a well-behaved endpoint, but there is no upper bound on page count or accumulated rows.

If the LFX user-service ever returns a full page while ignoring the `offset` query param (a plausible legacy-API behavior) and reports `TotalSize: 0` or an incorrect total, the loop never terminates and the `users` slice grows without bound — an unbounded-memory / hung-request failure mode for a single enrichment lookup.

## Suggested direction

Add a sane ceiling (e.g. a max page count or max total rows, logged as a warning/error if hit) so a misbehaving endpoint degrades to a bounded partial result instead of hanging the sync/web-bff request indefinitely.

## Origin

Surfaced during PR #157 post-merge issue triage, while verifying #161 was fixed by `d453defd`.

Start in lfx/client.go at Client.SearchUsers and trace the offset pagination introduced by #161 and commit d453defd. Decide on a bounded page or row limit, including how a warning or error is reported when it is reached. Done means a misbehaving endpoint returns a bounded partial result instead of hanging or growing users without limit.

Written by the indexing model from the issue text.