feat(moderation): add chat bans list endpoint with admin access checks

app/chats/repository.py

@@ -434,3 +434,10 @@ async def remove_chat_ban(db: AsyncSession, *, chat_id: int, user_id: int) -> No
     ban = await get_chat_ban(db, chat_id=chat_id, user_id=user_id)
     if ban:
         await db.delete(ban)
+
+
+async def list_chat_bans(db: AsyncSession, *, chat_id: int) -> list[ChatBan]:
+    result = await db.execute(
+        select(ChatBan).where(ChatBan.chat_id == chat_id).order_by(ChatBan.created_at.desc(), ChatBan.id.desc())
+    )
+    return list(result.scalars().all())