#30 INT-1: RunFlow Binding Sync

Implement /v1/runflow/bindings CRUD. Map stage completions to RunFlow node_ref. Call RunFlow approve/reject on terminal decision states using bulkman. Handle sync errors. (UB-RF-1, EV-RF-1, EV-RF-2, EV-RF-3, EV-RF-4, OP-RF-1)