feat: queue voice session cover generation jobs

backend/app/services/voice_session_service.py

@@ -31,7 +31,7 @@ from app.services.memory_service import build_enhanced_memory_context
 from app.services.provider_router import generate_story_content, text_to_speech
 from app.services.story_service import (
     create_story_from_result,
-    generate_story_cover,
+    queue_story_asset_generation,
     validate_profile_and_universe,
 )
 from app.services.voice_session_safety import (
@@ -1710,15 +1710,21 @@ async def finalize_voice_session_service(
     generation_job_id: str | None = None
     if request.generate_cover and story.cover_prompt:
         try:
-            await generate_story_cover(story.id, user_id, db)
+            cover_job = await queue_story_asset_generation(
+                story.id,
+                user_id,
+                ["image"],
+                db,
+            )
+            generation_job_id = str(cover_job["id"])
             await _record_session_event(
                 db,
                 session_id=session.id,
                 turn_id=None,
-                event_type="session_cover_generation_succeeded",
+                event_type="session_cover_generation_queued",
                 status="succeeded",
-                message="Finalized story cover was generated after session save.",
-                metadata={"story_id": story.id},
+                message="Finalized story cover generation was queued after session save.",
+                metadata={"story_id": story.id, "generation_job_id": generation_job_id},
             )
         except HTTPException as exc:
             await _record_session_event(
@@ -1727,11 +1733,11 @@ async def finalize_voice_session_service(
                 turn_id=None,
                 event_type="session_cover_generation_failed",
                 status="failed",
-                message="Finalized story cover generation failed after session save.",
+                message="Finalized story cover generation failed before the worker could start.",
                 metadata={"story_id": story.id, "error": str(exc.detail)},
             )
             logger.warning(
-                "voice_session_finalize_cover_failed",
+                "voice_session_finalize_cover_queue_failed",
                 session_id=session.id,
                 story_id=story.id,
                 error=str(exc.detail),