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/telegram.ts

@@ -6,6 +6,20 @@
 
 import type { TelegramThemeParams } from './theme';
 
+/** TelegramPopupButton is one button of a native showPopup (Bot API 6.2). */
+export interface TelegramPopupButton {
+  id?: string;
+  type?: 'default' | 'ok' | 'close' | 'cancel' | 'destructive';
+  text?: string;
+}
+
+/** TelegramPopupParams configures a native showPopup (title optional, message required, up to 3 buttons). */
+export interface TelegramPopupParams {
+  title?: string;
+  message: string;
+  buttons?: TelegramPopupButton[];
+}
+
 interface TelegramWebApp {
   initData: string;
   initDataUnsafe?: { start_param?: string };
@@ -51,6 +65,8 @@ interface TelegramWebApp {
     getItem?: (key: string, cb: (err: string | null, value?: string) => void) => void;
     setItem?: (key: string, value: string, cb?: (err: string | null, ok?: boolean) => void) => void;
   };
+  showConfirm?: (message: string, cb?: (ok: boolean) => void) => void;
+  showPopup?: (params: TelegramPopupParams, cb?: (buttonId: string) => void) => void;
 }
 
 function webApp(): TelegramWebApp | undefined {
@@ -347,6 +363,34 @@ export function telegramCloudSet(key: string, value: string): Promise<void> {
   });
 }
 
+/** telegramDialogsAvailable reports whether Telegram's native dialogs (showConfirm / showPopup, Bot
+ *  API 6.2) are usable, so a caller can choose the native path over its own modal. */
+export function telegramDialogsAvailable(): boolean {
+  return !!webApp()?.showPopup;
+}
+
+/**
+ * telegramShowConfirm shows Telegram's native confirm dialog and resolves true when the user
+ * accepts. Resolves false outside Telegram or on a client predating the dialog, so callers should
+ * gate on telegramDialogsAvailable and fall back to their own modal otherwise.
+ */
+export function telegramShowConfirm(message: string): Promise<boolean> {
+  const w = webApp();
+  if (!w?.showConfirm) return Promise.resolve(false);
+  return new Promise((resolve) => w.showConfirm!(message, (ok) => resolve(!!ok)));
+}
+
+/**
+ * telegramShowPopup shows Telegram's native popup and resolves the pressed button id (the empty
+ * string when dismissed without pressing a button). Resolves null outside Telegram or on a client
+ * predating the popup, so callers can fall back to their own modal.
+ */
+export function telegramShowPopup(params: TelegramPopupParams): Promise<string | null> {
+  const w = webApp();
+  if (!w?.showPopup) return Promise.resolve(null);
+  return new Promise((resolve) => w.showPopup!(params, (id) => resolve(id ?? '')));
+}
+
 /** Haptic is the set of feedbacks the app triggers. */
 export type Haptic = 'select' | 'success' | 'error' | 'warning' | 'light' | 'medium' | 'heavy';