refactor(api): TOML 配置 SSOT、统一错误契约、Auth/事务加固与可观测性 (#33)

配置 SSOT（TOML + .env）
统一错误契约
Auth 与事务边界
Redis / Celery 可靠性:业务 Redis（DB/0）与 Celery broker/backend（DB/1）显式拆分；连接池、sync client
可观测性（OpenTelemetry + LGTM）

api/app/features/memoir/schemas.py

@@ -1,4 +1,45 @@
-from pydantic import BaseModel
+from pydantic import BaseModel, ConfigDict, Field
+
+from app.agents.state_schema import MemoirStateSchema as MemoirStateResponse
+
+__all__ = [
+    "BookResponse",
+    "ChapterDetailResponse",
+    "ChapterListItemResponse",
+    "CoverGenerationResponse",
+    "ExportPdfRequest",
+    "ExportPdfResponse",
+    "ImageAssetResponse",
+    "MemoirStateResponse",
+    "NextQuestionContextResponse",
+    "ReadingSegmentResponse",
+    "SetChapterStoryOrderRequest",
+    "StatusMessageResponse",
+    "StoryOrderResponse",
+    "UpdateBookRequest",
+]
+
+
+class ImageAssetResponse(BaseModel):
+    placeholder: str = ""
+    description: str = ""
+    index: int = 0
+    status: str = "pending"
+    prompt: str | None = None
+    url: str | None = None
+    provider: str | None = None
+    style: str | None = None
+    size: str | None = None
+    error: str | None = None
+    retryable: bool | None = None
+    created_at: str | None = None
+    updated_at: str | None = None
+
+
+class ReadingSegmentResponse(BaseModel):
+    story_id: str
+    body_markdown: str = ""
+    cover_asset: ImageAssetResponse | None = None
 
 
 class UpdateBookRequest(BaseModel):
@@ -14,3 +55,75 @@ class SetChapterStoryOrderRequest(BaseModel):
     """按顺序绑定本章节要收录的 stories（覆盖原有 chapter_story_links）。"""
 
     story_ids: list[str]
+
+
+class BookResponse(BaseModel):
+    id: str | None = None
+    title: str | None = None
+    total_pages: int | None = None
+    total_words: int | None = None
+    cover_image_url: str | None = None
+    has_update: bool | None = None
+    last_update_chapter_id: str | None = None
+    message: str | None = None
+
+
+class StatusMessageResponse(BaseModel):
+    status: str
+    message: str | None = None
+
+
+class ExportPdfResponse(BaseModel):
+    pdf_base64: str
+    filename: str
+
+
+class ChapterListItemResponse(BaseModel):
+    model_config = ConfigDict(extra="ignore")
+
+    id: str
+    title: str | None = None
+    category: str | None = None
+    order_index: int | None = None
+    status: str = "draft"
+    summary: str = ""
+    canonical_markdown: str = ""
+    cover_asset: ImageAssetResponse | None = None
+    images: list[ImageAssetResponse] = Field(default_factory=list)
+    word_count: int = 0
+    updated_at: str | None = None
+    is_new: bool = False
+    source_segments: list[str] = Field(default_factory=list)
+
+
+class ChapterDetailResponse(BaseModel):
+    model_config = ConfigDict(extra="ignore")
+
+    id: str
+    title: str | None = None
+    canonical_markdown: str = ""
+    order_index: int | None = None
+    status: str | None = None
+    category: str | None = None
+    images: list[ImageAssetResponse] = Field(default_factory=list)
+    cover_asset: ImageAssetResponse | None = None
+    reading_segments: list[ReadingSegmentResponse] = Field(default_factory=list)
+    updated_at: str | None = None
+    is_new: bool = False
+    source_segments: list[str] = Field(default_factory=list)
+
+
+class CoverGenerationResponse(BaseModel):
+    triggered: list[str] = Field(default_factory=list)
+
+
+class StoryOrderResponse(BaseModel):
+    status: str
+    chapter_id: str
+    story_count: int
+
+
+class NextQuestionContextResponse(BaseModel):
+    current_stage: str | None = None
+    empty_slots: list[str] = Field(default_factory=list)
+    covered_stages: list[str] = Field(default_factory=list)