Update dependency @types/bull to v3.15.1

Editor assessment

Updating @types/bull to v3.15.1 states the dependency and target version precisely, and chore(deps) matches the routine bump in type and scope. The subject alone identifies the change; no diff is needed. There is no body, appropriate for a type-definition refresh, and no footers appear, none being owed. Hygiene is clean: imperative mood, no trailing period, compact subject, no ticket junk, no pasted material. One complete line for a one-line-kind of change — the communication is exactly proportionate and entirely unambiguous.