Repeated /stock_portfolio calls stacked a random-token pending key per
call, and applying the dividend cleaned up only the pressed one — the
rest kept live buttons until the TTL sweep. Keys are now deterministic
(pending-dividend:<userID>:<eventID>) so re-suggesting overwrites the
previous action, retires the old message's button, and applying leaves
exactly one key to delete. Callback data carries <userID>:<eventID>
instead of a token; presses are still validated against the stored
owner, chat, and message binding.
tiennm99
bd0ad6b817