[Bugfix] Route.reference field is missing private modifier

[EnduranceCode]

Description

The reference field in Route.java (line 76) has no access modifier, making it package-private instead of private. All other fields in the Route entity and in other entity classes (e.g. RouteSegment, DeviceTelemetry, TrackerAccount) are declared as private.

The field should be declared as private.

File affected:

• endurancetrio-data/src/main/java/com/endurancetrio/data/tracker/model/entity/Route.java

Acceptance Criteria

• The reference field is changed from package-private to private
• All existing getter/setter methods continue to work correctly
• The project builds and existing tests pass without errors