argus's review on this PR noted the insert loop recomputed new
Set(drink_ids) instead of reusing uniqueIds from the existence check
above — same result (deterministic dedup), just needless duplication.
Hoisted uniqueIds out of the existence-check block so both call sites
share it.
Verified: tsc --noEmit and server build clean; re-ran the live smoke
test (dup drink_ids dedup to the right set, nonexistent drink_id still
400s).
a7ec25997f