Refactor current team methods to use add/update item

Replaced direct upsert_item calls with add_item and update_item in set_current_team and update_current_team methods for improved abstraction and consistency.

Author: Fr4nc3

src/backend/common/database/cosmosdb.py

@@ -454,12 +454,10 @@ async def get_current_team(self, user_id: str, team_id: str) -> UserCurrentTeam:
     async def set_current_team(self, current_team: UserCurrentTeam) -> None:
         """Set the current team for a user."""
         await self._ensure_initialized()
+        await self.add_item(current_team)
 
 
-        await self.container.upsert_item(current_team.dict())
     async def update_current_team(self, current_team: UserCurrentTeam) -> None:
         """Update the current team for a user."""
         await self._ensure_initialized()
-
-
-        await self.container.upsert_item(current_team.dict())
+        await self.update_item(current_team)