chore: merge upstream main into the upgrade branch
The branch predated the official-image migration (coop-cloud/discourse#16), so its merge-base was 0.8.1+3.5.0 and the PR's file list re-showed that migration's changes as if this PR introduced them. The branch TREE already matched upstream; only its history lacked those commits. Recording the merge leaves the PR's diff as what it actually changes: app 3.5.3 -> 2026.7.1 and redis 7.4-alpine -> 8.10-alpine. Conflict in compose.yml resolved in favour of the branch (both sides edited the same image lines; the branch already carries upstream's official-image switch plus the version bumps). Resulting tree is byte-identical to the pre-merge branch tree.
This commit is contained in: