feat: add integration tests for project and scenario lifecycles, update templates to new Starlette signature, and optimize project retrieval logic

services/repositories.py

@@ -40,7 +40,10 @@ class ProjectRepository:
         stmt = select(Project).where(Project.id == project_id)
         if with_children:
             stmt = stmt.options(joinedload(Project.scenarios))
-        project = self.session.execute(stmt).scalar_one_or_none()
+        result = self.session.execute(stmt)
+        if with_children:
+            result = result.unique()
+        project = result.scalar_one_or_none()
         if project is None:
             raise EntityNotFoundError(f"Project {project_id} not found")
         return project