feat: add OSRM road-snapping for GPS routes and mileage (#21)

Routes now follow actual roads instead of cutting through buildings:
- New OsrmService calls free OSRM Match API to snap GPS points to roads
- Position history endpoint accepts ?matched=true for road-snapped geometry
- Stats use OSRM road distance instead of Haversine crow-flies distance
- Frontend shows solid blue polylines for matched routes, dashed for raw
- Handles chunking (100 coord limit), rate limiting, graceful fallback
- Distance badge shows accurate road miles on route trails

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

backend/src/gps/gps.controller.ts

@@ -132,6 +132,7 @@ export class GpsController {
 
   /**
    * Get a driver's location history (for route trail display)
+   * Query param 'matched=true' returns OSRM road-snapped route
    */
   @Get('locations/:driverId/history')
   @Roles(Role.ADMINISTRATOR)
@@ -139,9 +140,17 @@ export class GpsController {
     @Param('driverId') driverId: string,
     @Query('from') fromStr?: string,
     @Query('to') toStr?: string,
+    @Query('matched') matched?: string,
   ) {
     const from = fromStr ? new Date(fromStr) : undefined;
     const to = toStr ? new Date(toStr) : undefined;
+
+    // If matched=true, return OSRM road-matched route
+    if (matched === 'true') {
+      return this.gpsService.getMatchedRoute(driverId, from, to);
+    }
+
+    // Otherwise return raw GPS points
     return this.gpsService.getDriverLocationHistory(driverId, from, to);
   }