feat(profile): account-deletion flow + terminal deleted screen

Profile gains a Delete-account control (durable accounts) opening a step-up dialog: a
mailed code for an email account, or the typed DELETE phrase for a platform-only one.
On success the app swaps to a terminal AccountDeleted screen ('Учётная запись удалена')
with a Close that closes the host Mini App (telegramClose / vkClose; web = no close).
Wires deleteRequest/deleteConfirm through client/transport/mock/codec; ru/en i18n;
codec wire test + Chromium/WebKit e2e.

ui/src/lib/app.svelte.ts

@@ -13,6 +13,7 @@ import { startLocalEvalMetrics } from './localeval-metrics';
 import { applyReduceMotion, applyTelegramTheme, applyTheme, type ThemePref, type TelegramThemeParams } from './theme';
 import {
   insideTelegram,
+  telegramClose,
   collectTelegramDiag,
   type TelegramDiag,
   onTelegramPath,
@@ -32,7 +33,7 @@ import {
   telegramCloudGet,
   telegramCloudSet,
 } from './telegram';
-import { onVKPath, insideVK, vkInit, vkDisableSwipeBack, vkLaunchParams, vkUserName, vkStartParam, vkOnScheme, vkOnInsets, vkSetViewSettings, appearanceForBg } from './vk';
+import { onVKPath, insideVK, vkInit, vkClose, vkDisableSwipeBack, vkLaunchParams, vkUserName, vkStartParam, vkOnScheme, vkOnInsets, vkSetViewSettings, appearanceForBg } from './vk';
 import { haptic } from './haptics';
 import { CLOUD_PREFS_KEY, decodeClientPrefs, encodeClientPrefs } from './cloudprefs';
 import { parseStartParam } from './deeplink';
@@ -92,6 +93,9 @@ export const app = $state<{
   /** The caller's active manual block, or null. When set, App.svelte replaces every screen with
    *  the terminal blocked screen and all push/poll is stopped. */
   blocked: BlockStatus | null;
+  /** Set once the account has been deleted: App.svelte shows the terminal "account deleted"
+   *  screen and all push/poll is stopped. Reopening the app just creates a fresh account. */
+  accountDeleted: boolean;
   toast: Toast | null;
   lastEvent: PushEvent | null;
   theme: ThemePref;
@@ -140,6 +144,7 @@ export const app = $state<{
   session: null,
   profile: null,
   blocked: null,
+  accountDeleted: false,
   toast: null,
   lastEvent: null,
   theme: 'auto',
@@ -544,6 +549,39 @@ export async function applyLinkResult(r: LinkResult): Promise<void> {
   void persistLanguageToServer(app.locale);
 }
 
+/**
+ * requestDeleteAccount starts account deletion and reports which step-up the account uses:
+ * 'email' (a code was mailed) or 'phrase' (type the confirmation phrase).
+ */
+export async function requestDeleteAccount(): Promise<'email' | 'phrase'> {
+  return (await gateway.deleteRequest()).method;
+}
+
+/**
+ * confirmDeleteAccount confirms deletion with the mailed code or the typed phrase. On
+ * success it switches to the terminal "account deleted" screen and stops all push/poll; it
+ * throws on a bad code/phrase so the caller can let the user retry.
+ */
+export async function confirmDeleteAccount(code: string, phrase: string): Promise<void> {
+  await gateway.deleteConfirm(code, phrase);
+  closeStream();
+  app.accountDeleted = true;
+}
+
+/**
+ * closeDeletedApp closes the host Mini App from the terminal deleted screen (Telegram / VK).
+ * A plain browser has nothing to close, so it is a no-op there — the terminal screen stays.
+ */
+export function closeDeletedApp(): void {
+  if (insideTelegram()) {
+    telegramClose();
+    return;
+  }
+  if (insideVK()) {
+    void vkClose();
+  }
+}
+
 /**
  * syncTelegramChrome paints Telegram's header/background/bottom bar from the app's live
  * theme tokens, so the surrounding chrome matches the UI. Called after the theme is applied.