fix: trip builder handles NULL-GPS speed-only rows (BUG-16 follow-up)

Trips starting/ending on speed-only rows violated the trips.*GPSX NOT NULL
constraint. Use the first/last GPS-bearing row for start/end coordinates, and
skip a trip that never got any GPS fix (no location to record).

modules/app_trip.py

@@ -198,16 +198,28 @@ def build_trip_summaries(raw_rows):
         if not any(event["obd"] for event in events) and duration_seconds < 10:
             continue
 
+        # Speed-only rows (logged before the first GPS fix) have NULL coords.
+        # Use the first/last row that actually has a position for start/end GPS,
+        # and skip a trip that never got any fix at all (no location to record).
+        gps_rows = [
+            r for r in trip_rows
+            if r["latitude"] is not None and r["longitude"] is not None
+        ]
+        if not gps_rows:
+            continue
+        start_gps = gps_rows[0]
+        end_gps = gps_rows[-1]
+
         trips.append({
             "id": start["id"],
             "start_tracking_id": start["id"],
             "end_tracking_id": end["id"],
             "start_datetime": start["datetime"].isoformat(sep=" "),
             "end_datetime": end["datetime"].isoformat(sep=" "),
-            "start_gpsx": start["latitude"],
+            "start_gpsx": start_gps["latitude"],
-            "start_gpsy": start["longitude"],
+            "start_gpsy": start_gps["longitude"],
-            "end_gpsx": end["latitude"],
+            "end_gpsx": end_gps["latitude"],
-            "end_gpsy": end["longitude"],
+            "end_gpsy": end_gps["longitude"],
             "distance_km": round(distance_km, 3),
             "duration_seconds": duration_seconds,
             "point_count": len(trip_rows),

tests/test_app_trip.py

@@ -115,7 +115,7 @@ class TripBuilderTest(unittest.TestCase):
         self.assertEqual(trips[0]["start_tracking_id"], 1)
         self.assertEqual(trips[0]["end_tracking_id"], 5)
 
-    def test_speed_only_rows_without_gps_build_trip(self):
+    def test_speed_only_rows_without_any_gps_are_skipped(self):
         started = datetime(2026, 1, 1, 8)
         rows = [
             (index + 1, started + timedelta(seconds=index * 5), None, None, 30)
@@ -124,12 +124,27 @@ class TripBuilderTest(unittest.TestCase):
 
         trips = app_trip.build_trip_summaries(rows)
 
+        # No GPS fix at all -> no location to record -> no trip (the speed-only
+        # rows remain in the DB but can't form a geolocated trip).
+        self.assertEqual(len(trips), 0)
+
+    def test_speed_only_start_uses_first_gps_fix_for_start_coords(self):
+        started = datetime(2026, 1, 1, 8)
+        rows = [
+            (1, started, None, None, 30),
+            (2, started + timedelta(seconds=5), None, None, 30),
+            (3, started + timedelta(seconds=10), 45.5000, -73.5000, 30),
+            (4, started + timedelta(seconds=15), 45.5001, -73.5000, 30),
+            (5, started + timedelta(seconds=20), 45.5002, -73.5000, 30),
+        ]
+
+        trips = app_trip.build_trip_summaries(rows)
+
         self.assertEqual(len(trips), 1)
         self.assertEqual(trips[0]["start_tracking_id"], 1)
-        self.assertEqual(trips[0]["end_tracking_id"], 4)
+        self.assertEqual(trips[0]["end_tracking_id"], 5)
-        self.assertEqual(trips[0]["distance_km"], 0)
+        self.assertEqual(trips[0]["start_gpsx"], 45.5)
-        self.assertEqual(trips[0]["max_speed_kmh"], 30)
+        self.assertEqual(trips[0]["start_gpsy"], -73.5)
-        self.assertEqual(trips[0]["point_count"], 4)
 
     def test_clock_rollback_does_not_merge_motion_episodes(self):
         first = self.rows_for_route(