feat(telegram): native dialogs for confirms and deep-link notices

Inside the Mini App, route the destructive confirmations (resign, block, unfriend)
through Telegram's native showConfirm, and present the deep-link info modals (stale
invite, welcome-on-redeem) as a native showPopup whose button opens the bot chat.
Outside Telegram, or on a client predating the dialogs, the existing in-app Modal is
used unchanged; offline also keeps the modal so the action retains its disabled state.

Adds showConfirm/showPopup wrappers to telegram.ts and a pure popup-params builder
(nativedialogs.ts) with unit tests; the deep-link modal components choose native vs
in-app via an effect gated on insideTelegram + dialog availability.

ui/src/screens/Friends.svelte

@@ -7,7 +7,7 @@
   import { GatewayError } from '../lib/client';
   import { t } from '../lib/i18n/index.svelte';
   import { friendCodeParam, shareLink } from '../lib/deeplink';
-  import { shareTelegramLink } from '../lib/telegram';
+  import { insideTelegram, shareTelegramLink, telegramDialogsAvailable, telegramShowConfirm } from '../lib/telegram';
   import type { AccountRef, FriendCode, RobotBlockEntry } from '../lib/model';
 
   let friends = $state<AccountRef[]>([]);
@@ -66,20 +66,36 @@
 
   // confirmBlock / confirmUnfriend run the pending action once its modal is
   // accepted, then clear the target and the revealed row.
-  function confirmBlock(): void {
-    const target = blockTarget;
+  function confirmBlock(target = blockTarget): void {
     blockTarget = null;
     revealedId = null;
     if (target) void blockUser(target.accountId);
   }
 
-  function confirmUnfriend(): void {
-    const target = unfriendTarget;
+  function confirmUnfriend(target = unfriendTarget): void {
     unfriendTarget = null;
     revealedId = null;
     if (target) void remove(target.accountId);
   }
 
+  // onBlockClick / onUnfriendClick: inside the Mini App (and online) confirm with Telegram's native
+  // dialog and act on accept; otherwise open the in-app confirm modal (the offline / web path).
+  async function onBlockClick(f: AccountRef): Promise<void> {
+    if (connection.online && insideTelegram() && telegramDialogsAvailable()) {
+      if (await telegramShowConfirm(`${t('friends.blockConfirm')}\n${f.displayName}`)) confirmBlock(f);
+      return;
+    }
+    blockTarget = f;
+  }
+
+  async function onUnfriendClick(f: AccountRef): Promise<void> {
+    if (connection.online && insideTelegram() && telegramDialogsAvailable()) {
+      if (await telegramShowConfirm(`${t('friends.unfriendConfirm')}\n${f.displayName}`)) confirmUnfriend(f);
+      return;
+    }
+    unfriendTarget = f;
+  }
+
   // While a friend row is slid open, a tap anywhere outside its action buttons
   // closes it again. Taps on a kebab are skipped so its own toggle stays in charge.
   $effect(() => {
@@ -216,8 +232,8 @@
           {#each friends as f (f.accountId)}
             <div class="rowwrap" class:revealed={revealedId === f.accountId}>
               <div class="acts">
-                <button class="iconbtn" onclick={() => (blockTarget = f)} disabled={!connection.online} aria-label={t('friends.block')}>🚫</button>
-                <button class="iconbtn" onclick={() => (unfriendTarget = f)} disabled={!connection.online} aria-label={t('friends.unfriend')}>✖️</button>
+                <button class="iconbtn" onclick={() => onBlockClick(f)} disabled={!connection.online} aria-label={t('friends.block')}>🚫</button>
+                <button class="iconbtn" onclick={() => onUnfriendClick(f)} disabled={!connection.online} aria-label={t('friends.unfriend')}>✖️</button>
               </div>
               <div class="row">
                 <span class="who">{f.displayName}</span>
@@ -264,7 +280,7 @@
         <p class="confirm-name">{blockTarget.displayName}</p>
         <div class="confirm-row">
           <button class="cancel" onclick={() => (blockTarget = null)}>{t('common.cancel')}</button>
-          <button class="danger" onclick={confirmBlock} disabled={!connection.online}>{t('friends.block')}</button>
+          <button class="danger" onclick={() => confirmBlock()} disabled={!connection.online}>{t('friends.block')}</button>
         </div>
       </Modal>
     {/if}
@@ -273,7 +289,7 @@
         <p class="confirm-name">{unfriendTarget.displayName}</p>
         <div class="confirm-row">
           <button class="cancel" onclick={() => (unfriendTarget = null)}>{t('common.cancel')}</button>
-          <button class="danger" onclick={confirmUnfriend} disabled={!connection.online}>{t('friends.unfriend')}</button>
+          <button class="danger" onclick={() => confirmUnfriend()} disabled={!connection.online}>{t('friends.unfriend')}</button>
         </div>
       </Modal>
     {/if}