feat: Add combined track functionality with repository and service layers

- Introduced CombinedTrackModel, CombinedTrackCreate, and CombinedTrackRepository for managing combined tracks.
- Implemented logic to create combined tracks based on existing tracks between two stations.
- Added methods to check for existing combined tracks and retrieve constituent track IDs.
- Enhanced TrackModel and TrackRepository to support OSM ID and track updates.
- Created migration scripts for adding combined tracks table and OSM ID to tracks.
- Updated services and API endpoints to handle combined track operations.
- Added tests for combined track creation, repository methods, and API interactions.

backend/app/models/__init__.py

@@ -8,11 +8,14 @@ from .auth import (
     UserPublic,
 )
 from .base import (
+    CombinedTrackCreate,
+    CombinedTrackModel,
     StationCreate,
     StationModel,
     StationUpdate,
     TrackCreate,
     TrackModel,
+    TrackUpdate,
     TrainCreate,
     TrainModel,
     TrainScheduleCreate,
@@ -33,9 +36,12 @@ __all__ = [
     "StationUpdate",
     "TrackCreate",
     "TrackModel",
+    "TrackUpdate",
     "TrainScheduleCreate",
     "TrainCreate",
     "TrainModel",
     "UserCreate",
     "to_camel",
+    "CombinedTrackCreate",
+    "CombinedTrackModel",
 ]