feat(privacy): add private-message permission toggle

app/chats/service.py

@@ -104,6 +104,12 @@ async def create_chat_for_user(db: AsyncSession, *, creator_id: int, payload: Ch
             detail="Private chat requires exactly one target user.",
         )
     if payload.type == ChatType.PRIVATE:
+        target_user = await get_user_by_id(db, member_ids[0])
+        if target_user and not target_user.allow_private_messages:
+            raise HTTPException(
+                status_code=status.HTTP_403_FORBIDDEN,
+                detail="User does not accept private messages",
+            )
         if await has_block_relation_between_users(db, user_a_id=creator_id, user_b_id=member_ids[0]):
             raise HTTPException(
                 status_code=status.HTTP_403_FORBIDDEN,