fix: improve GPS position sync reliability and add route trails (#21)

Backend:
- Increase sync overlap buffer from 5s to 30s to catch late-arriving positions
- Add position history endpoint GET /gps/locations/:driverId/history
- Add logging for position sync counts (returned vs inserted)

Frontend:
- Add useDriverLocationHistory hook for fetching position trails
- Draw Polyline route trails on GPS map for each tracked driver
- Historical positions shown as semi-transparent paths behind live markers

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/hooks/useGps.ts

@@ -123,6 +123,24 @@ export function useDriverLocation(driverId: string) {
   });
 }
 
+/**
+ * Get driver location history (for route trail display)
+ */
+export function useDriverLocationHistory(driverId: string | null, from?: string, to?: string) {
+  return useQuery<Array<{ latitude: number; longitude: number; speed: number; timestamp: Date }>>({
+    queryKey: ['gps', 'locations', driverId, 'history', from, to],
+    queryFn: async () => {
+      const params = new URLSearchParams();
+      if (from) params.append('from', from);
+      if (to) params.append('to', to);
+      const { data } = await api.get(`/gps/locations/${driverId}/history?${params}`);
+      return data;
+    },
+    enabled: !!driverId,
+    refetchInterval: 30000, // Refresh every 30 seconds
+  });
+}
+
 /**
  * Get driver stats
  */