Route planning for Berlin public transport (BVG) using the v6.bvg.transport.rest API. Use when the user asks for: (1) route suggestions between two addresses or stops, (2) live next-departure info for a stop, (3) arrival-time–based journey planning (arrive-by or depart-at). Supports outputting 2–3 options ranked by travel time, transfers, and walking, and returning step-by-step directions and refresh tokens for live updates.