Review fixes #2: bigger flag star, TG header below nav, board-tile relocation

Addressing the review on #23:
- Flag star scaled up ~25% (the hammer&sickle emblem unchanged, kept clear of it).
- TG fullscreen header: drop the WHOLE header below the content-safe-area top
  inset (the hamburger stays to the right of the title), instead of pinning the
  hamburger to the physical top edge.
- DnD: a placed (pending) tile can now be relocated by dragging it to another
  board cell (board->board); it lifts off its source cell while dragged; and it
  can be grabbed even on the zoomed board (touch-action:none on the pending
  cell, so the drag wins over the board pan). The manual-selection blue frame
  now clears on recall.

ui/public/flag-ussr.svg

@@ -1,7 +1,7 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 16" role="img" aria-label="СССР">
   <rect width="24" height="16" fill="#cc0000"/>
-  <!-- small five-pointed star -->
-  <path fill="#ffd700" d="M6 1.9 L6.32 2.86 7.33 2.87 6.51 3.47 6.82 4.43 6 3.84 5.18 4.43 5.49 3.47 4.67 2.87 5.68 2.86 Z"/>
+  <!-- five-pointed star (scaled up ~25% around its centre per review) -->
+  <path fill="#ffd700" transform="translate(6 3.17) scale(1.25) translate(-6 -3.17)" d="M6 1.9 L6.32 2.86 7.33 2.87 6.51 3.47 6.82 4.43 6 3.84 5.18 4.43 5.49 3.47 4.67 2.87 5.68 2.86 Z"/>
   <g fill="none" stroke="#ffd700" stroke-linecap="round" stroke-linejoin="round" transform="translate(6.8 6) scale(0.667) translate(-6.8 -6)">
     <!-- sickle: a crescent blade + short handle, mirrored across a diagonal through its centre
          so it reads as the canonical sickle (blade sweeping down-right); the hammer is untouched -->