fix(vk): friend-code link as ?hash, Android safe-area via bridge insets, landscape home-bar colour

Contour review of the VK Bridge group:

- #6 invite link: VK's documented '#' direct-link payload is eaten by the vk.com SPA before it
  reaches the app, so the friend-code link now carries the payload as a query param
  (vk.com/app<id>?hash=f<code>); the recipient already reads the `hash` query param (vkStartParam).
  (Whether VK forwards the '?' through to the iframe is being confirmed on the contour.)
- #8 Android: the VK mobile webview does not surface the home-bar inset via CSS env() (config
  insets are iOS-only), so subscribe to the bridge insets (VKWebAppUpdateConfig + VKWebAppUpdateInsets)
  and set --tg-safe-* to max(env(), the VK value).
- #8 landscape colour: the home-indicator strip was the (grey) page background because the two-pane
  landscape game has no bottom bar. The left-panel controls bar now paints its own chrome into the
  inset (Screen gains a selfInset flag that drops the shell's detached padding strip), and the
  game-land runs flush to the edge.

Verified: svelte-check, 347 unit, build, bundle-gate; the landscape safe-area painting reproduced in
the mock (controls bar + board reach the edge, strip takes the bar colour). The VK-Bridge / VK launch
behaviours (Android insets, the ?hash forward) need the live contour.

ui/src/game/Game.svelte

@@ -1074,6 +1074,7 @@
   column
   scroll={false}
   tabbar={landscape ? undefined : bottomBar}
+  selfInset={landscape}
 >
   {#if view}
     {#if landscape}
@@ -1738,8 +1739,10 @@
     grid-template-columns: clamp(260px, 32%, 360px) 1fr;
     gap: 4px;
     /* The left-column children carry their own horizontal --pad (matching portrait), so the
-       grid only pads its right edge; the board centres in the right pane. */
-    padding: 4px var(--pad) 6px 0;
+       grid only pads its right edge; the board centres in the right pane. The bottom is flush so the
+       controls bar and the board reach the screen edge — the controls bar owns the home-indicator
+       inset (see the .leftpane .tabbar rule), the board runs under the thin indicator. */
+    padding: 4px var(--pad) 0 0;
     overflow: hidden;
   }
   .leftpane {
@@ -1747,6 +1750,13 @@
     flex-direction: column;
     min-height: 0;
   }
+  /* The home-indicator inset on the controls side: the left panel's controls bar paints its own
+     chrome (--bg-elev) into it so the buttons clear the cut-out (the shell's detached content strip
+     is suppressed here via Screen selfInset); the board pane runs to the edge under the thin
+     indicator. */
+  .game-land .leftpane :global(.tabbar) {
+    padding-bottom: calc(8px + var(--tg-safe-bottom, 0px));
+  }
   .rightpane {
     /* A size container spanning the whole right area: the board (Board.svelte's .viewport.land)
        fills it and fits the square board by HEIGHT via min(100cqw,100cqh); on zoom-in the board