refactor: 优化后端路由功能

- 扩展books.py路由，添加新接口
- 优化websocket.py路由，增强WebSocket功能

api/routers/books.py

@@ -55,6 +55,44 @@ async def clear_book_update(
     return {"status": "ok"}
 
 
+class UpdateBookRequest(BaseModel):
+    title: str
+    subtitle: str | None = None  # 目前数据库不支持subtitle，但保留字段以便将来扩展
+
+
+@router.put("/{book_id}")
+async def update_book(
+    book_id: str,
+    request: UpdateBookRequest = Body(...),
+    current_user: UserModel = Depends(get_current_user),
+    db: AsyncSession = Depends(get_async_db)
+):
+    """更新书籍标题（需要认证，只能更新自己的回忆录）"""
+    book = await db.get(BookModel, book_id)
+    if not book:
+        raise HTTPException(status_code=404, detail="Book not found")
+    
+    # 验证用户权限
+    if book.user_id != current_user.id:
+        raise HTTPException(status_code=403, detail="无权更新此回忆录")
+    
+    # 更新标题
+    book.title = request.title
+    # subtitle字段目前数据库不支持，暂时忽略
+    await db.commit()
+    await db.refresh(book)
+    
+    return {
+        "id": book.id,
+        "title": book.title,
+        "total_pages": book.total_pages,
+        "total_words": book.total_words,
+        "cover_image_url": book.cover_image_url,
+        "has_update": book.has_update,
+        "last_update_chapter_id": book.last_update_chapter_id,
+    }
+
+
 class ExportPdfRequest(BaseModel):
     book_id: str