fix(01): calendar slot merge in OutputReview for PN/Schwartz badges

GenerateResponse now includes calendar field from backend.
OutputReview merges CalendarSlot into PostResult via slot_index,
enabling BadgePN, BadgeSchwartz rendering and Retry button.

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

backend/services/generation_pipeline.py

@@ -198,6 +198,7 @@ class GenerationPipeline:
             total=status.total,
             success_count=success_count,
             failed_count=failed_count,
+            calendar=status.calendar,
         )
 
     def generate_single(