Common enemy rework

backend/app/schemas/assignment.py

@@ -48,3 +48,14 @@ class DropResult(BaseModel):
     penalty: int
     total_points: int
     new_drop_count: int
+
+
+class EventAssignmentResponse(BaseModel):
+    """Response for event-specific assignment (Common Enemy)"""
+    assignment: AssignmentResponse | None
+    event_id: int | None
+    challenge_id: int | None
+    is_completed: bool
+
+    class Config:
+        from_attributes = True