feat: add unified generation entrypoint

backend/app/schemas/story_schemas.py

@@ -29,6 +29,19 @@ class GenerateRequest(BaseModel):
     universe_id: str | None = None
 
 
+class GenerationRequest(BaseModel):
+    """Unified generation request for story and storybook outputs."""
+
+    output_mode: Literal["story", "storybook"] = Field(default="story")
+    type: Literal["keywords", "full_story"] = Field(default="keywords")
+    data: str = Field(..., min_length=1, max_length=MAX_DATA_LENGTH)
+    education_theme: str | None = Field(default=None, max_length=MAX_EDU_THEME_LENGTH)
+    generate_images: bool = Field(default=True)
+    page_count: int = Field(default=6, ge=4, le=12)
+    child_profile_id: str | None = None
+    universe_id: str | None = None
+
+
 class StoryResponse(StoryStatusMixin):
     """Story generation response."""
 
@@ -99,6 +112,25 @@ class StorybookResponse(StoryStatusMixin):
     cover_url: str | None = None
 
 
+class GenerationResponse(StoryStatusMixin):
+    """Unified generation response for the target workflow API."""
+
+    id: int
+    title: str
+    mode: str
+    story_text: str | None = None
+    pages: list[StorybookPageResponse] | None = None
+    cover_prompt: str | None = None
+    image_url: str | None = None
+    cover_url: str | None = None
+    audio_ready: bool = False
+    errors: dict[str, str | None] = Field(default_factory=dict)
+    main_character: str | None = None
+    art_style: str | None = None
+    child_profile_id: str | None = None
+    universe_id: str | None = None
+
+
 class StoryDetailResponse(StoryStatusMixin):
     """Story detail response for both stories and storybooks."""