Stage 17 round 6 (cluster 1): profile, tap flash, variant naming, chat/nudge by turn

- Profile: drop the hint-balance line.
- Board: no mobile tap flash on a cell tap (-webkit-tap-highlight-color: transparent),
  matching the web click; the only intentional cell animation stays the last-word flash.
- Variant names keyed by the game's alphabet, not the UI language: english -> Scrabble
  always, russian_scrabble -> Скрэббл always (unlocalized, never collide), erudit localized.
- Chat/nudge are mutually exclusive by turn: the message field + Send show on your turn,
  the nudge replaces them on the opponent's turn; while the nudge cooldown is active the
  button is disabled with a grey 'awaiting reply' caption to its left.

ui/src/game/Game.svelte

@@ -760,7 +760,7 @@
 
 {#if panel === 'chat'}
   <Modal title={t('game.chat')} onclose={() => (panel = 'none')}>
-    <Chat {messages} myId={app.session?.userId ?? ''} {busy} canNudge={!isMyTurn && !nudgeOnCooldown} onsend={sendChat} onnudge={nudge} />
+    <Chat {messages} myId={app.session?.userId ?? ''} {busy} myTurn={isMyTurn} {nudgeOnCooldown} onsend={sendChat} onnudge={nudge} />
   </Modal>
 {/if}