feat(ui): auto-confirm the email deeplink on load

Drop the confirm button: the /confirm screen confirms the token as soon as it
loads. The token rides the URL fragment (never sent to the server), so a plain link
prefetch cannot reach it, and the manual six-digit code is the fallback if an
aggressive scanner runs the page. Update the ARCHITECTURE/FUNCTIONAL wording
accordingly and swap the confirm.prompt/action strings for confirm.busy (en+ru).

ui/src/lib/i18n/en.ts

@@ -36,8 +36,7 @@ export const en = {
   'login.sendCode': 'Send code',
   'login.codePlaceholder': '6-digit code',
   'login.signIn': 'Sign in',
-  'confirm.prompt': 'Confirm your email to finish.',
-  'confirm.action': 'Confirm',
+  'confirm.busy': 'Confirming your email…',
   'confirm.linked': 'Email confirmed.',
   'confirm.merge': 'Almost done — finish the merge in the app.',
   'confirm.close': 'You can close this window and return to the game.',

ui/src/lib/i18n/ru.ts

@@ -37,8 +37,7 @@ export const ru: Record<MessageKey, string> = {
   'login.sendCode': 'Отправить код',
   'login.codePlaceholder': 'Код из 6 цифр',
   'login.signIn': 'Войти',
-  'confirm.prompt': 'Подтвердите почту, чтобы завершить.',
-  'confirm.action': 'Подтвердить',
+  'confirm.busy': 'Подтверждаем почту…',
   'confirm.linked': 'Почта подтверждена.',
   'confirm.merge': 'Почти готово — завершите объединение в приложении.',
   'confirm.close': 'Можно закрыть это окно и вернуться в игру.',

ui/src/screens/Confirm.svelte

@@ -1,37 +1,35 @@
 <script lang="ts">
+  import { onMount } from 'svelte';
   import { confirmDeeplink } from '../lib/app.svelte';
   import { t } from '../lib/i18n/index.svelte';
 
   let { token }: { token: string } = $props();
-  // idle → busy → (login navigates away) | linked | merge | error. The token is
-  // confirmed only on the button press (a POST), so a mail scanner prefetching the
-  // link (a GET on the SPA route) never consumes it.
-  let stage = $state<'idle' | 'busy' | 'linked' | 'merge' | 'error'>('idle');
+  // The token rides the URL fragment (#/confirm/<token>), which is never sent to the
+  // server, so a plain link prefetch cannot reach it — confirm as soon as the screen
+  // loads. The manual 6-digit code in the same email is the fallback if an aggressive
+  // scanner ever runs the page and consumes the single-use token first.
+  let stage = $state<'busy' | 'linked' | 'merge' | 'error'>('busy');
 
-  async function confirm(): Promise<void> {
+  onMount(async () => {
     if (!token) {
       stage = 'error';
       return;
     }
-    stage = 'busy';
     try {
+      // A login navigates into the app; a link stays here with a result.
       const r = await confirmDeeplink(token);
-      // A login has already navigated into the app; a link stays here with a result.
       stage = r === 'merge_required' ? 'merge' : 'linked';
     } catch {
       stage = 'error';
     }
-  }
+  });
 </script>
 
 <main class="confirm">
   <div class="card">
     <div class="brand">{t('app.title')}</div>
-    {#if stage === 'idle' || stage === 'busy'}
-      <p>{t('confirm.prompt')}</p>
-      <button class="primary" disabled={stage === 'busy'} onclick={confirm}>
-        {t('confirm.action')}
-      </button>
+    {#if stage === 'busy'}
+      <p class="muted">{t('confirm.busy')}</p>
     {:else if stage === 'linked'}
       <p class="ok">{t('confirm.linked')}</p>
       <p class="muted">{t('confirm.close')}</p>
@@ -81,15 +79,4 @@
   .err {
     color: var(--danger, #c0392b);
   }
-  button {
-    padding: 12px;
-    border-radius: var(--radius-sm);
-    border: 1px solid var(--accent);
-    font-weight: 600;
-    background: var(--accent);
-    color: var(--accent-text);
-  }
-  button:disabled {
-    opacity: 0.5;
-  }
 </style>