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/screens/Profile.svelte

@@ -1,7 +1,15 @@
 <script lang="ts">
   import { onMount } from 'svelte';
   import Modal from '../components/Modal.svelte';
-  import { app, applyLinkResult, handleError, logout, showToast } from '../lib/app.svelte';
+  import {
+    app,
+    applyLinkResult,
+    confirmDeleteAccount,
+    handleError,
+    logout,
+    requestDeleteAccount,
+    showToast,
+  } from '../lib/app.svelte';
   import { GatewayError } from '../lib/client';
   import { connection } from '../lib/connection.svelte';
   import { gateway } from '../lib/gateway';
@@ -43,6 +51,10 @@
   let changingEmail = $state(false);
   // A pending unlink awaiting the confirmation dialog (email is never unlinked).
   let confirmUnlink = $state<null | { kind: 'telegram' | 'vk'; label: string }>(null);
+  // The account-deletion step-up dialog: null when closed, else the required proof method.
+  let deleting = $state<null | { method: 'email' | 'phrase' }>(null);
+  let deleteCode = $state('');
+  let deletePhrase = $state('');
   const telegramLinkable = loginWidgetAvailable();
 
   function defaultTz(): string {
@@ -235,6 +247,29 @@
       handleError(e);
     }
   }
+
+  // startDelete opens the deletion dialog, asking the backend which step-up the account uses
+  // (a mailed code for an email account, or a typed phrase for a platform-only one).
+  async function startDelete() {
+    try {
+      const method = await requestDeleteAccount();
+      deleteCode = '';
+      deletePhrase = '';
+      deleting = { method };
+    } catch (e) {
+      handleError(e);
+    }
+  }
+
+  async function doDelete() {
+    if (!deleting) return;
+    try {
+      // On success the app swaps to the terminal "account deleted" screen (app.accountDeleted).
+      await confirmDeleteAccount(deleteCode.trim(), deletePhrase.trim());
+    } catch (e) {
+      handleError(e);
+    }
+  }
 </script>
 
 <div class="page">
@@ -381,6 +416,10 @@
       {/if}
     </section>
 
+    {#if !p.isGuest}
+      <button class="deletebtn" onclick={startDelete} disabled={!connection.online}>{t('profile.deleteAccount')}</button>
+    {/if}
+
     <!-- Logout is hidden for now but kept wired — drop `hidden` to re-enable
          once its entry point is decided; logout() also still runs on an invalid session. -->
     <button class="logout" hidden onclick={() => logout()}>{t('login.title')} / logout</button>
@@ -409,6 +448,28 @@
   </Modal>
 {/if}
 
+{#if deleting}
+  {@const d = deleting}
+  <Modal title={t('profile.deleteTitle')} onclose={() => (deleting = null)}>
+    <p class="warn">{t('profile.deleteWarn')}</p>
+    {#if d.method === 'email'}
+      <p class="muted">{t('profile.deleteEmailPrompt')}</p>
+      <div class="addrow">
+        <input class="codein" bind:value={deleteCode} placeholder={t('profile.emailCode')} inputmode="numeric" maxlength="6" />
+      </div>
+    {:else}
+      <p class="muted">{t('profile.deletePhrasePrompt')}</p>
+      <div class="addrow">
+        <input bind:value={deletePhrase} placeholder={t('profile.deletePhrasePlaceholder')} autocapitalize="characters" />
+      </div>
+    {/if}
+    <div class="addrow end">
+      <button class="ghost" onclick={() => (deleting = null)}>{t('common.cancel')}</button>
+      <button class="btn danger" onclick={doDelete} disabled={!connection.online}>{t('profile.deleteConfirm')}</button>
+    </div>
+  </Modal>
+{/if}
+
 <style>
   .page {
     padding: var(--pad);
@@ -614,6 +675,18 @@
   .ghost:disabled {
     opacity: 0.5;
   }
+  .deletebtn {
+    margin-top: 8px;
+    align-self: flex-start;
+    padding: 8px 14px;
+    border: 1px solid var(--danger, #c0392b);
+    background: transparent;
+    color: var(--danger, #c0392b);
+    border-radius: var(--radius-sm);
+  }
+  .deletebtn:disabled {
+    opacity: 0.5;
+  }
   .logout {
     margin-top: 8px;
     align-self: flex-start;