Game/Telegram review polish: USSR flag, touch drag ghost, TG fullscreen header

Backlog item 2 of ~4 (owner review pass):
- USSR flag emblem redrawn (canonical hammer & sickle, scaled down 1.5x
  below the star).
- Touch drag-and-drop: enlarge the drag ghost 1.5x on touch only (the finger
  hides the tile); suppress the iOS tap-highlight that lingered on a rack tile
  sliding into a dragged tile's slot.
- Telegram fullscreen: its native nav no longer hides our header -- the header
  drops below the content-safe-area top inset and the menu (hamburger) lifts
  into the nav band, centred (--tg-content-top from the SDK inset + a
  tg-fullscreen class; new telegram.ts helper + app wiring).

Tests: UI check/test:unit/build + full e2e (60) green. The iOS tap-highlight
fix and the TG-fullscreen layout want on-device verification on the deploy.

ui/src/game/Rack.svelte

@@ -91,6 +91,10 @@
     font-size: 1.4rem;
     touch-action: none;
     user-select: none;
+    -webkit-user-select: none;
+    /* iOS shows a tap/active highlight that can linger on the neighbour sliding into a
+       dragged tile's slot (Stage 17); suppress it so only our own styles mark a tile. */
+    -webkit-tap-highlight-color: transparent;
   }
   .tile.selected {
     outline: 3px solid var(--accent);