Toast new events into the Event Log button

When the Event Log is collapsed, a freshly-arrived event now flashes as
a toast anchored above the button, then animates down and fades into it.
Suppressed on the initial state load and on rollback reseeds so it only
fires for genuinely new events; clicking the toast opens the log.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

TODO.md

@@ -18,7 +18,7 @@
 
 - [x] The back button on the admin page should go back to the active game, not the join screen
 
-- [ ] Add a toast pop-up for new events entering the event log, that then fades into the event log button
+- [x] Add a toast pop-up for new events entering the event log, that then fades into the event log button
 
 - [ ] When you get a gat, there should be a pop up to enter a description of it, as with your name