Refactor set_tell_positions logic with updated rules.

Revised the set_tell_positions endpoint to handle updated business rules for puck positioning. Improved event handling to ensure proper nullification, updates, and removal of tell_positions based on the provided payload. Enhanced query performance and normalized puck name processing for consistency.

backend/app/schemas.py

@@ -645,7 +645,8 @@ class PuckWithTellPosition(BaseModel):
     puck_type: str
     puck_location_in_dewar: Optional[str]
     dewar_id: int
-    samples: List[Sample]
+    samples: Optional[List[Sample]] = None
+    tell_position: Optional[str]
 
     class Config:
         from_attributes = True