Sync update notification message after each relevant action

[Salvialf]

Summary

• Fix message::removeAll('update', 'newUpdate') in install/update.php that never deleted anything: message::save() randomizes the logicalId when it equals 'newUpdate', so no message ever had that logicalId in the database.
• Add update::refreshUpdateMessage() as a central method to manage the update notification message lifecycle: removes stale messages when the pending list changes, leverages message::save() native dedup to avoid spurious toasts when the list is unchanged, and cleans up entirely when no updates are pending.
• Call refreshUpdateMessage() after every operation that can change update statuses: jeedom::cronHourly() and the update, checkUpdate, checkAllUpdate actions in update.ajax.php.