Journey: show actual transfer/layover time between legs

Replaces the generic "1x umsteigen" summary with the real gap per
transfer (e.g. "SchnellBus S20 ->13min-> Regionalzug RB 67"), computed
from each leg's estimated (falling back to planned) arrival/departure.
Falls back to a plain "umsteigen" label when EFA doesn't supply both
timestamps for a given transfer.

screens/journey.py

@@ -275,6 +275,16 @@ class JourneyScreen(Screen):
                         if title and title not in notice_titles:
                             notice_titles.append(title)
 
+            # Layover between consecutive legs: next leg's (estimated,
+            # falling back to planned) departure minus this leg's (likewise)
+            # arrival. None when either side is missing a timestamp, so the
+            # render step can fall back to a plain "umsteigen" label.
+            transfer_minutes = []
+            for cur, nxt in zip(legs, legs[1:]):
+                arr = _parse_time(cur["destination"].get("arrivalTimeEstimated")) or _parse_time(cur["destination"].get("arrivalTimePlanned"))
+                dep = _parse_time(nxt["origin"].get("departureTimeEstimated")) or _parse_time(nxt["origin"].get("departureTimePlanned"))
+                transfer_minutes.append(max(0, int((dep - arr).total_seconds() // 60)) if arr and dep else None)
+
             # EFA returns UTC timestamps (Z suffix) -- astimezone() with no
             # args converts to the system's local timezone before display.
             # Without this, times showed 2h behind (CEST is UTC+2), making
@@ -285,6 +295,7 @@ class JourneyScreen(Screen):
                 "arrival": arr_actual.astimezone().strftime("%H:%M") if arr_actual else "--:--",
                 "legs": [{"name": leg["line"], "mode": leg["mode"]} for leg in legs],
                 "transfers": len(legs) - 1,
+                "transfer_minutes": transfer_minutes,
                 "platform": (first["origin"].get("properties") or {}).get("platformName") or "",
                 "notice": "; ".join(notice_titles),
             })
@@ -389,11 +400,11 @@ class JourneyScreen(Screen):
 
                 shown = draw_segment(leg["name"], avail=right_edge - cursor_x)
                 if idx < len(journey["legs"]) - 1 and cursor_x < right_edge and shown == leg["name"]:
-                    draw_segment(" → ", avail=right_edge - cursor_x)
+                    gap = journey["transfer_minutes"][idx]
+                    sep = f" →{gap}min→ " if gap is not None else " → umsteigen → "
+                    draw_segment(sep, avail=right_edge - cursor_x)
 
             trailing_parts = []
-            if journey["transfers"] > 0:
-                trailing_parts.append(f"{journey['transfers']}x umsteigen")
             if journey["platform"]:
                 trailing_parts.append(f"Gl. {journey['platform']}")
             if trailing_parts and cursor_x < right_edge: