style(lobby): bold the score line, a touch smaller

Per owner follow-up: the whole lobby score line is now bold (font-weight 700,
matching the over-the-board score plaques) and a hair smaller (0.8rem) to offset
the heavier weight. The viewer's own number keeps its green/red standing tint.

ui/src/screens/Lobby.svelte

@@ -478,8 +478,13 @@
     font-size: 0.85rem;
     color: var(--text-muted);
   }
+  /* The score line is bold and a touch smaller than the surrounding muted sub-text. */
+  .scoreline {
+    font-weight: 700;
+    font-size: 0.8rem;
+  }
   /* The viewer's own number on an in-progress game: green when leading or tied, red when
-     losing. Other numbers and the separators keep the muted .sub colour; no bold. */
+     losing; other numbers and the separators keep the muted .sub colour. */
   .num.win {
     color: var(--ok);
   }