Backport of #42321 to release/2026.6.
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## Summary
Topic bookmark creation, listing, search, and reminder eligibility now
require the first post to be visible to the user. The fix adds an inner
join on the first post with hidden-post filtering to the list query and
delegates creation and visibility checks to `guardian.can_see_post?` on
the first post, preventing an authenticated user from bookmarking a
topic or searching its metadata after the first post is hidden.
## Source
- Patch Triage: https://patch.discourse.org/patch-triage/1530
Co-authored-by: discourse-patch-triage
<272280883+discourse-patch-triage[bot]@users.noreply.github.com>
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Co-authored-by: Chris Alberti <christo@discourse.org>
d32c1381a5
