Add dedicated endpoint to assign a route to a region

PUT /api/routes/{id}/region assigns/reassigns an existing route to a
region directly, validating the target region exists and is active.
Stands in for the blocked assignAreaToRegion until an Area entity
exists between Region and Route.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Distribution/Features/Route/RouteService.cs

@@ -2,7 +2,7 @@ using Distribution.Infra.UoW;
 
 namespace Distribution.Features.Route;
 
-public class RouteService(IRouteRepository repo, IUnitOfWork uow)
+public class RouteService(IRouteRepository repo, Region.IRegionRepository regionRepo, IUnitOfWork uow)
 {
     public async Task<List<RouteResponse>> GetAllAsync() =>
         (await repo.GetAllAsync())
@@ -64,6 +64,29 @@ public class RouteService(IRouteRepository repo, IUnitOfWork uow)
         return new RouteResponse(route.Id, route.FK_RegionId, route.RouteName, route.StartPoint, route.EndPoint, route.Length, route.IsActive, route.CreatedAt);
     }
 
+    public async Task<RouteResponse?> AssignToRegionAsync(Guid id, AssignRouteToRegionRequest request, CancellationToken ct = default)
+    {
+        var route = await repo.GetByIdAsync(id);
+        if (route is null || !route.IsActive) return null;
+
+        var region = await regionRepo.GetByIdAsync(request.RegionId);
+        if (region is null || !region.IsActive) return null;
+
+        route.FK_RegionId = request.RegionId;
+        await uow.BeginAsync(ct);
+        try
+        {
+            repo.Update(route);
+            await uow.CommitAsync(ct);
+        }
+        catch
+        {
+            await uow.RollbackAsync(ct);
+            throw;
+        }
+        return new RouteResponse(route.Id, route.FK_RegionId, route.RouteName, route.StartPoint, route.EndPoint, route.Length, route.IsActive, route.CreatedAt);
+    }
+
     public async Task<bool> DeleteAsync(Guid id, CancellationToken ct = default)
     {
         var route = await repo.GetByIdAsync(id);