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/lib/nativedialogs.test.ts

@@ -0,0 +1,25 @@
+import { describe, expect, it } from 'vitest';
+import { BOT_BUTTON_ID, botInfoPopup } from './nativedialogs';
+
+describe('botInfoPopup', () => {
+  it('inlines the bot handle and adds an open-bot button', () => {
+    const p = botInfoPopup('Title', 'Open the bot {bot} to play.', 'erudit_bot', 'OK');
+    expect(p.title).toBe('Title');
+    expect(p.message).toBe('Open the bot @erudit_bot to play.');
+    expect(p.buttons).toEqual([
+      { id: BOT_BUTTON_ID, text: '@erudit_bot' },
+      { id: 'ok', text: 'OK' },
+    ]);
+  });
+
+  it('drops the token and the open-bot button when no username is known', () => {
+    const p = botInfoPopup('Title', 'Open the bot {bot} to play.', '', 'OK');
+    expect(p.message).toBe('Open the bot to play.');
+    expect(p.buttons).toEqual([{ id: 'ok', text: 'OK' }]);
+  });
+
+  it('preserves newlines in the message', () => {
+    const p = botInfoPopup('Hi', 'Welcome!\n\nUse {bot} now.', 'b', 'OK');
+    expect(p.message).toBe('Welcome!\n\nUse @b now.');
+  });
+});