fix: give chatbot pickups per-leg surcharges including the return leg

docs/chatbot-mcp.md

@@ -58,6 +58,10 @@ Trip rules (`App\Chatbot\TripCatalog`):
 - `search_trips` only offers products that TYPO3 lists in its own website search (`searchable`) and does
   not mark as unbookable. Closed group trips and staff trainings are `searchable: false`. `get_trip` still
   answers when someone names their code.
+- Pickup surcharges are per person and per leg, so each pickup carries `surchargeOutbound`, `surchargeReturn` and
+  their sum `surchargeRoundTrip`. A single figure was read by the model as the whole price. A leg listed without a
+  price is `0`, because BusPro bills only priced legs; `surchargeReturn` is absent only where the point is not
+  served on the way back.
 - The export's `guide` (name, phone) and all BusPro ids are never output.
 
 `search_trips` mirrors the search page (`/skireisen/suche/`), whose data is TYPO3's import of our own