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/screens/Profile.svelte

@@ -166,8 +166,6 @@
       <div class="name">{p.displayName}</div>
       {#if p.isGuest}<span class="badge">{t('profile.guest')}</span>{/if}
 
-      <div class="hintbal"><span>{t('profile.hintBalance')}</span><b>{p.hintBalance}</b></div>
-
       {#if p.isGuest}
         <p class="muted">{t('profile.guestLocked')}</p>
       {:else}
@@ -284,15 +282,6 @@
     color: var(--text-muted);
     font-size: 0.8rem;
   }
-  .hintbal {
-    display: flex;
-    justify-content: space-between;
-    color: var(--text-muted);
-  }
-  .hintbal b {
-    color: var(--text);
-    font-weight: 600;
-  }
   .muted {
     color: var(--text-muted);
     font-size: 0.9rem;