fix(vk): friend-code link is the plain vk.com/app link (VK strips iframe query payload)

The contour diagnostic confirmed VK forwards only the signed vk_* params to the iframe — a
custom payload on the app link is dropped (the '#' eaten by the vk.com SPA, a '?' query
stripped), so the friend-code cannot ride the link. The VK share link is now just
vk.com/app<id>; the recipient enters the copied code by hand (VKWebAppCopyText works). The
vkStartParam reader + bootVK routing stay as a no-op, ready for a post-moderation channel.
Removes the temporary deep-link diagnostic.

ui/src/screens/Friends.svelte

@@ -201,8 +201,7 @@
         <button class="btn" onclick={redeem} disabled={!connection.online}>{t('friends.redeem')}</button>
       </div>
       {#if code}
-        {@const sharePayload = friendCodeParam(code.code)}
-        {@const shareUrl = insideVK() ? vkShareLink(sharePayload) : shareLink(sharePayload)}
+        {@const shareUrl = insideVK() ? vkShareLink() : shareLink(friendCodeParam(code.code))}
         <div class="code" data-testid="friend-code">
           <div class="coderow">
             <button class="codeval" onclick={copyCode}>{code.code}</button>