Mission: Decouple gateway from hardcoded Postgres/Valkey backends. 20 tasks across 5 phases. Estimated total: ~214K tokens. Phase 1: Interface extraction (4 tasks) Phase 2: Wrap existing backends as adapters (5 tasks) Phase 3: Local tier implementation (4 tasks) Phase 4: Config + CLI commands (4 tasks) Phase 5: Migration + docs (3 tasks)