Add unit tests for station service and enhance documentation

- Introduced unit tests for the station service, covering creation, updating, and archiving of stations.
- Added detailed building block view documentation outlining the architecture of the Rail Game system.
- Created runtime view documentation illustrating key user interactions and system behavior.
- Developed concepts documentation detailing domain models, architectural patterns, and security considerations.
- Updated architecture documentation to reference new detailed sections for building block and runtime views.

backend/app/models/__init__.py

@@ -10,6 +10,7 @@ from .auth import (
 from .base import (
     StationCreate,
     StationModel,
+    StationUpdate,
     TrackCreate,
     TrackModel,
     TrainCreate,
@@ -29,6 +30,7 @@ __all__ = [
     "UserPublic",
     "StationCreate",
     "StationModel",
+    "StationUpdate",
     "TrackCreate",
     "TrackModel",
     "TrainScheduleCreate",