fix: smooth GPS-derived replay speed to kill jitter spikes

route_points (Pi) and get_trip_route (server) derived GPS speed from a
single 5s segment, so GPS position jitter could read 150+ km/h when the car
wasn't going that fast. Both now average over a trailing ~30s window (same
as the max-speed calc), so spikes are damped.

modules/app_trip.py

@@ -285,12 +285,28 @@ def route_points(raw_rows, max_points=2000, odometer_baseline=0.0, prior_km=0.0)
     for index, row in enumerate(rows):
         row["speed_source"] = "obd" if row["speed"] > 0 else "gps"
         if row["speed"] <= 0 and index:
-            distance_km, segment_speed = _segment(row, rows[index - 1])
-            row["speed"] = (
-                segment_speed
-                if distance_km * 1000 >= GPS_MOTION_METERS
-                else 0
-            )
+            # Derive GPS speed over a trailing ~30s window, not the raw 5s
+            # segment — a single segment can spike 100+ km/h on GPS jitter
+            # (same smoothing build_trip_summaries uses for max speed).
+            window_start = max(0, index - GPS_SPEED_WINDOW)
+            start_row = rows[window_start]
+            seconds = (
+                row["datetime"] - start_row["datetime"]
+            ).total_seconds()
+            if seconds > 0:
+                window_km = haversine_km(
+                    (start_row["latitude"], start_row["longitude"]),
+                    (row["latitude"], row["longitude"]),
+                )
+                window_speed = window_km / seconds * 3600
+                row["speed"] = (
+                    window_speed
+                    if window_km * 1000 >= GPS_MOTION_METERS
+                    and window_speed <= MAX_PLAUSIBLE_SPEED_KMH
+                    else 0
+                )
+            else:
+                row["speed"] = 0
         if index:
             segment_km, _ = _segment(row, rows[index - 1])
             cumulative_km += segment_km