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.

docs/UI_DESIGN.md

@@ -233,7 +233,12 @@ and a long message does not scroll.
 
 Lobby rows show two lines (opponents, then result + score) with a large place-based emoji
 on the right: Victory 🏆 / Defeat 🥈 / Draw 🏅, and for 3–4-player games II 🥈 / III 🥉 /
-IV 🏅; active games show Your move 🟢 / Opponent's move ⏳; invitations use 💌.
+IV 🏅; active games show Your move 🟢 / Opponent's move ⏳; invitations use 💌. When a listed
+game **becomes your turn or finishes** while the lobby is open, that status emoji **blinks
+twice** (a two-cycle opacity fade, ~2 s; suppressed under reduce-motion) to draw the eye — the
+opponent's-turn change is silent. Each card's blink is keyed by game id, so overlapping
+events animate in isolation, and the newest bottom toast cancels the previous one and replays
+its entrance (`components/Toast.svelte`, re-keyed on a per-message sequence).
 
 ## Social, account & history surfaces