feat: add generation job cancel and retry queue

backend/app/schemas/story_schemas.py

@@ -195,6 +195,8 @@ class GenerationJobSummaryResponse(BaseModel):
     progress_percent: int
     progress_label: str
     is_terminal: bool
+    can_cancel: bool = False
+    can_retry: bool = False
     result_snapshot: dict[str, Any] = Field(default_factory=dict)
     error_message: str | None = None
     created_at: datetime