fix: add is_flow_synced and source_tree_name to step list response

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/schemas/step_library.py

@@ -82,6 +82,8 @@ class StepLibraryListResponse(BaseModel):
     created_by: UUID
     author_name: Optional[str] = None
     created_at: datetime
+    is_flow_synced: bool = False
+    source_tree_name: Optional[str] = None
 
     class Config:
         from_attributes = True