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/Board.svelte

@@ -250,6 +250,9 @@
     border-radius: 1px;
     background: var(--cell-bg);
     color: var(--prem-text);
+    /* No mobile tap flash on a cell tap (parity with the web click; the only intentional
+       cell animation is the last-word .flash highlight). */
+    -webkit-tap-highlight-color: transparent;
     padding: 0;
     overflow: hidden;
     font-size: 0;