feat: 章节软删除、对话左滑删除，移除已读状态

- 章节：详情页增加删除按钮，软删除（is_active=False），AI 不再修改但保留供参考
- 章节：get_chapter 增加 is_active 校验，已删除章节返回 404
- 章节：AI 生成时参考同类别已删除章节摘要
- 对话：左滑显示删除，调用 hard delete API，删除前二次确认
- 对话：根布局包裹 GestureHandlerRootView 以支持 Swipeable
- 对话：移除已读/未读状态展示及相关 i18n

api/app/features/memoir/repo.py

@@ -2,7 +2,7 @@
 
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
-from sqlalchemy.orm import joinedload
+from sqlalchemy.orm import Session, joinedload
 
 from app.features.memoir.models import Book, Chapter, ChapterSection, MemoirState
 
@@ -56,3 +56,33 @@ async def get_memoir_state(user_id: str, db: AsyncSession) -> MemoirState | None
     stmt = select(MemoirState).where(MemoirState.user_id == user_id)
     result = await db.execute(stmt)
     return result.scalar_one_or_none()
+
+
+def get_archived_chapter_summaries_sync(
+    session: Session, user_id: str, category: str
+) -> list[tuple[str, str]]:
+    """获取已删除（is_active=False）的同类别章节的标题与内容摘要，供 AI 参考。"""
+    stmt = (
+        select(Chapter)
+        .where(
+            Chapter.user_id == user_id,
+            Chapter.category == category,
+            Chapter.is_active == False,  # noqa: E712
+        )
+        .options(joinedload(Chapter.sections))
+        .order_by(Chapter.updated_at.desc())
+    )
+    result = session.execute(stmt)
+    chapters = list(result.unique().scalars().all())
+    summaries: list[tuple[str, str]] = []
+    for ch in chapters:
+        sections = getattr(ch, "sections", None) or []
+        parts = [
+            (s.content or "").strip()
+            for s in sorted(sections, key=lambda x: getattr(x, "order_index", 0))
+        ]
+        combined = "".join(parts)
+        preview = (combined[:200] + "...") if len(combined) > 200 else combined
+        if preview.strip():
+            summaries.append((ch.title or "", preview))
+    return summaries