fix(system-tests): the member picker is given time to answer

[ExtraToast]

What

CommitteeManagerPageSystemTest flakes. The option click in CommitteeFormHelper.addMember now carries an explicit 20s budget instead of Playwright's 5s default.

Why

Reproduced locally against a CI-image stack:

creates committee from manager() FAILED
  TimeoutError: Timeout 5000ms exceeded
  waiting for getByRole(AriaRole.OPTION, ...setName("Create197509 Member")).first()
  at CommitteeFormHelper.addMember(CommitteeFormHelper.kt:42)

UserSelect debounces typing for SETTLE_MS = 250 and then makes an API round trip. The default budget starts running before either has happened, so a loaded runner exhausts it.

Three forced re-runs of the class pass after the change.

What this does not cover

The CI symptom I first saw was a different test in the same class — updates committee name and description, where the submit click produced no browser request at all. That symptom has not been reproduced locally and may be a separate path through save(). Calling it out rather than claiming the class is now clean.

The UserSelect unit tests here are guards, not a fix: they pass on main, and pin that a chosen member's id survives a list that cannot yet account for it.

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Diff breakdown — █ added ░ removed, scaled to the largest row.

frontend                                          +100     -1    3
  unit tests         █████████████████             +40     -0    1
  e2e tests          █████████████████████████░    +60     -1    2

system-tests                                       +34     -4    2
  system tests       ██████████████░░              +34     -4    2

──────────────────────────────────────────────────────────────────
production                                          +0     -0
tests                                             +134     -5
total (hand-written)                              +134     -5  5 files