User search previously filtered bots only when they happened to match the
search string. That produced two bad behaviours:
1. Bots owned by other users could surface on an exact-username match,
leaking them into assignee pickers and similar UI.
2. A user could not reliably find their own bots by typing a partial
name, so bots became awkward to assign to tasks.
Change ListUsers to treat bot ownership explicitly: the existing match
branch excludes rows owned by someone else, and a second branch always
returns bots owned by the calling user. The own-bots branch also
respects any AdditionalCond passed in so project-scoped listings don't
start leaking bots from outside the project.
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