feat(nudge): name the sender; blink lobby cards; re-animate toasts

The "waiting for your move" popup was the nudge (chat.nudge), shown without a
sender name. Resolve the nudger's per-game seat name server-side and carry it on
a new NudgeEvent.sender_name field, so:

- the in-app toast reads "<opponent>: Waiting for your move 🤭" (chat.nudgeBy);
- the out-of-app Telegram push names the sender too (render nudgeBy);

falling back to the plain phrase when the name is absent (RU mirrored). The
your_turn toast already named the opponent and is unchanged.

Lobby: when a card transitions into "your turn" or "finished" while the lobby is
open, its status emoji blinks twice (two 1s fades); the opponent's-turn change
stays in place. Blink state is keyed by game id (SvelteSet + per-id nonce/timer)
so overlapping events animate in isolation; suppressed under reduce-motion.

Toast: a per-message seq re-keys Toast.svelte, so the freshest toast cancels the
previous one and replays its entrance, uniformly on every screen.

Tests: notify.Nudge round-trip + render named/fallback (Go), game.Service.SeatName
(integration), codec/i18n/gamePhase/shouldBlink (UI). Docs (FUNCTIONAL +_ru,
UI_DESIGN) + PLAN TODO-7 (deferred FLIP card-relocation animation) updated.

ui/src/lib/codec.test.ts

@@ -54,6 +54,24 @@ describe('codec', () => {
     expect(decodeDraftView(b.asUint8Array())).toBe('{"x":1}');
   });
 
+  it('decodes a nudge event carrying the sender name', () => {
+    const b = new Builder(64);
+    const gid = b.createString('g1');
+    const from = b.createString('u2');
+    const name = b.createString('Ann');
+    fb.NudgeEvent.startNudgeEvent(b);
+    fb.NudgeEvent.addGameId(b, gid);
+    fb.NudgeEvent.addFromUserId(b, from);
+    fb.NudgeEvent.addSenderName(b, name);
+    b.finish(fb.NudgeEvent.endNudgeEvent(b));
+    expect(decodeEvent('nudge', b.asUint8Array())).toEqual({
+      kind: 'nudge',
+      gameId: 'g1',
+      fromUserId: 'u2',
+      senderName: 'Ann',
+    });
+  });
+
   it('round-trips a feedback submit and decodes state + unread', () => {
     const att = new Uint8Array([1, 2, 3, 4]);
     const req = fb.FeedbackSubmitRequest.getRootAsFeedbackSubmitRequest(