feat(chats): add per-user pinned chats and pinned sorting

app/chats/repository.py

@@ -70,7 +70,11 @@ def _user_chats_query(user_id: int, query: str | None = None) -> Select[tuple[Ch
                 Chat.type.cast(String).ilike(q),
             )
         )
-    return stmt.order_by(Chat.id.desc())
+    return stmt.order_by(
+        func.coalesce(ChatUserSetting.pinned, False).desc(),
+        ChatUserSetting.pinned_at.desc().nullslast(),
+        Chat.id.desc(),
+    )
 
 
 async def list_user_chats(
@@ -103,7 +107,11 @@ async def list_archived_user_chats(
             (ChatUserSetting.chat_id == Chat.id) & (ChatUserSetting.user_id == user_id),
         )
         .where(ChatMember.user_id == user_id, ChatUserSetting.archived.is_(True))
-        .order_by(Chat.id.desc())
+        .order_by(
+            func.coalesce(ChatUserSetting.pinned, False).desc(),
+            ChatUserSetting.pinned_at.desc().nullslast(),
+            Chat.id.desc(),
+        )
         .limit(limit)
     )
     if before_id is not None:
@@ -287,3 +295,28 @@ async def upsert_chat_archived_setting(
     db.add(setting)
     await db.flush()
     return setting
+
+
+async def upsert_chat_pinned_setting(
+    db: AsyncSession,
+    *,
+    chat_id: int,
+    user_id: int,
+    pinned: bool,
+) -> ChatUserSetting:
+    setting = await get_chat_user_setting(db, chat_id=chat_id, user_id=user_id)
+    if setting:
+        setting.pinned = pinned
+        setting.pinned_at = func.now() if pinned else None
+        await db.flush()
+        return setting
+    setting = ChatUserSetting(
+        chat_id=chat_id,
+        user_id=user_id,
+        archived=False,
+        pinned=pinned,
+        pinned_at=func.now() if pinned else None,
+    )
+    db.add(setting)
+    await db.flush()
+    return setting