Fix dark theme scrollbar colors customizations pages - #333634

PR classified as team-member.

✅ Head commit 3079e0d is a GitHub-created merge of the base branch into the PR branch. The merge content is exactly a clean 3-way merge of its parents, and the underlying PR-branch commit is signed by houghj16 with trusted key AD09C36591964284C805AB0758907753B66F4322 — credit inherited via 3079e0d → bfaca54. Approval requirement reduced from 2 to 1.

✅ Collaborator approvals: 2/1 (hawkticehurst, lszomoru).

✅ No newly added runnable binary files.

✅ No protected engineering system files changed.