chore: add OSRM-related type definitions for GPS routes

Adds distanceMethod to DriverStatsDto and LocationHistoryResponse interface
to support the OSRM road-snapping feature.

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

backend/src/gps/dto/location-response.dto.ts

@@ -33,6 +33,7 @@ export class DriverStatsDto {
     averageSpeedMph: number;
     totalTrips: number;
     totalDrivingMinutes: number;
+    distanceMethod?: string; // 'osrm' or 'haversine'
   };
   recentLocations: LocationDataDto[];
 }