feat(ui): real friend-invite share with a per-bot link

The friend-code 'share' was an <a> that just opened the bot. Make it a real share:
Telegram's native share-to-chat picker inside the Mini App (openTelegramLink +
t.me/share/url), the system share sheet (navigator.share) on the web, else copy the
link. The shared deep link points at the same bot the player is in — it picks
VITE_TELEGRAM_LINK_EN/_RU by the session's service language, falling back to the
single VITE_TELEGRAM_LINK. Adds the per-bot build args across Dockerfile / compose /
ci.yaml / .env / docs; PLAN TODO-5 updated.

ui/src/screens/Friends.svelte

@@ -5,6 +5,7 @@
   import { gateway } from '../lib/gateway';
   import { t } from '../lib/i18n/index.svelte';
   import { friendCodeParam, shareLink } from '../lib/deeplink';
+  import { shareTelegramLink } from '../lib/telegram';
   import type { AccountRef, FriendCode } from '../lib/model';
 
   let friends = $state<AccountRef[]>([]);
@@ -78,6 +79,28 @@
       // Clipboard may be unavailable (insecure context); leave the code on screen.
     }
   }
+
+  // shareInvite shares the friend-code deep link: inside Telegram via the native
+  // "share to chat" picker; on the web via the system share sheet; failing both, it
+  // copies the link to the clipboard.
+  async function shareInvite(url: string) {
+    const text = t('friends.inviteText');
+    if (shareTelegramLink(url, text)) return;
+    if (typeof navigator !== 'undefined' && navigator.share) {
+      try {
+        await navigator.share({ text, url });
+        return;
+      } catch {
+        return; // the user dismissed the share sheet
+      }
+    }
+    try {
+      await navigator.clipboard.writeText(url);
+      showToast(t('friends.linkCopied'));
+    } catch {
+      // Clipboard unavailable (insecure context); nothing more to do.
+    }
+  }
 </script>
 
 <div class="page">
@@ -97,7 +120,7 @@
         <button class="btn" onclick={redeem} disabled={!connection.online}>{t('friends.redeem')}</button>
       </div>
       {#if code}
-        {@const tg = shareLink(friendCodeParam(code.code))}
+        {@const tg = shareLink(friendCodeParam(code.code), app.session?.serviceLanguage || app.locale)}
         <div class="code" data-testid="friend-code">
           <div class="coderow">
             <button class="codeval" onclick={copyCode}>{code.code}</button>
@@ -107,7 +130,7 @@
             {t('friends.codeHint')} · {t('friends.codeExpires', { time: codeTime(code.expiresAtUnix) })}
           </span>
           {#if tg}
-            <a class="link tgshare" href={tg} target="_blank" rel="noopener">{t('friends.shareTelegram')}</a>
+            <button type="button" class="link tgshare" onclick={() => shareInvite(tg)}>{t('friends.shareTelegram')}</button>
           {/if}
         </div>
       {:else}