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/gen/fbs/scrabblefb/nudge-event.ts

@@ -34,8 +34,15 @@ fromUserId(optionalEncoding?:any):string|Uint8Array|null {
   return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
 }
 
+senderName():string|null
+senderName(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+senderName(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
 static startNudgeEvent(builder:flatbuffers.Builder) {
-  builder.startObject(2);
+  builder.startObject(3);
 }
 
 static addGameId(builder:flatbuffers.Builder, gameIdOffset:flatbuffers.Offset) {
@@ -46,15 +53,20 @@ static addFromUserId(builder:flatbuffers.Builder, fromUserIdOffset:flatbuffers.O
   builder.addFieldOffset(1, fromUserIdOffset, 0);
 }
 
+static addSenderName(builder:flatbuffers.Builder, senderNameOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(2, senderNameOffset, 0);
+}
+
 static endNudgeEvent(builder:flatbuffers.Builder):flatbuffers.Offset {
   const offset = builder.endObject();
   return offset;
 }
 
-static createNudgeEvent(builder:flatbuffers.Builder, gameIdOffset:flatbuffers.Offset, fromUserIdOffset:flatbuffers.Offset):flatbuffers.Offset {
+static createNudgeEvent(builder:flatbuffers.Builder, gameIdOffset:flatbuffers.Offset, fromUserIdOffset:flatbuffers.Offset, senderNameOffset:flatbuffers.Offset):flatbuffers.Offset {
   NudgeEvent.startNudgeEvent(builder);
   NudgeEvent.addGameId(builder, gameIdOffset);
   NudgeEvent.addFromUserId(builder, fromUserIdOffset);
+  NudgeEvent.addSenderName(builder, senderNameOffset);
   return NudgeEvent.endNudgeEvent(builder);
 }
 }