feat: track generation jobs

backend/app/db/models.py

@@ -83,11 +83,88 @@ class Story(Base):
     child_profile: Mapped["ChildProfile | None"] = relationship("ChildProfile")
     story_universe: Mapped["StoryUniverse | None"] = relationship("StoryUniverse")
 
+    @property
+    def retryable_assets(self) -> list[str]:
+        """Assets that can be completed or retried from the current persisted state."""
+
+        assets: list[str] = []
+
+        image_is_busy_or_ready = self.image_status in {"ready", "generating"}
+        if not image_is_busy_or_ready:
+            if self.mode == "storybook":
+                pages = self.pages or []
+                has_missing_page_image = any(
+                    isinstance(page, dict)
+                    and page.get("image_prompt")
+                    and not page.get("image_url")
+                    for page in pages
+                )
+                if (self.cover_prompt and not self.image_url) or has_missing_page_image:
+                    assets.append("image")
+            elif self.cover_prompt:
+                assets.append("image")
+
+        audio_is_busy_or_ready = self.audio_status in {"ready", "generating"}
+        if self.story_text and not audio_is_busy_or_ready:
+            assets.append("audio")
+
+        return assets
+
 
 def _uuid() -> str:
     return str(uuid4())
 
 
+class GenerationJob(Base):
+    """User-visible generation attempt that can be inspected after the request returns."""
+
+    __tablename__ = "generation_jobs"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=_uuid)
+    user_id: Mapped[str] = mapped_column(
+        String(255), ForeignKey("users.id", ondelete="CASCADE"), nullable=False, index=True
+    )
+    story_id: Mapped[int | None] = mapped_column(
+        Integer, ForeignKey("stories.id", ondelete="SET NULL"), nullable=True, index=True
+    )
+    output_mode: Mapped[str] = mapped_column(String(32), nullable=False)
+    input_type: Mapped[str] = mapped_column(String(32), nullable=False)
+    status: Mapped[str] = mapped_column(String(32), nullable=False, default="running", index=True)
+    current_step: Mapped[str] = mapped_column(
+        String(64), nullable=False, default="request_accepted"
+    )
+    request_payload: Mapped[dict] = mapped_column(JSON, default=dict)
+    result_snapshot: Mapped[dict] = mapped_column(JSON, default=dict)
+    error_message: Mapped[str | None] = mapped_column(Text)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), index=True
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now()
+    )
+
+
+class GenerationJobEvent(Base):
+    """Append-only event emitted by a generation job."""
+
+    __tablename__ = "generation_job_events"
+
+    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+    job_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("generation_jobs.id", ondelete="CASCADE"), nullable=False, index=True
+    )
+    story_id: Mapped[int | None] = mapped_column(
+        Integer, ForeignKey("stories.id", ondelete="SET NULL"), nullable=True, index=True
+    )
+    event_type: Mapped[str] = mapped_column(String(64), nullable=False)
+    status: Mapped[str] = mapped_column(String(32), nullable=False)
+    message: Mapped[str | None] = mapped_column(Text)
+    event_metadata: Mapped[dict] = mapped_column(JSON, default=dict)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), index=True
+    )
+
+
 class ChildProfile(Base):
     """Child profile entity."""