UI: tab-bar navigation — drop the hamburger

Replace Menu.svelte (hamburger) everywhere with tab-bar navigation:
- Settings hub (SettingsHub) from the lobby ⚙️ tab: Settings/Profile/
  Friends/About as in-place tabs, back → lobby; the lobby ⚙️ badge counts
  incoming friend requests (invitations keep their own lobby section).
- Comms hub (CommsHub) from the move-history 💬: Chat/Dictionary tabs,
  back → game; Dictionary only while the game is active.
- Game menu items relocate into the open history: 🏁 leave / 📤 export in
  the header, 🤝 add-friend per opponent card, 💬 comms; unread chat is
  badged on the score bar + the 💬.
- TapConfirm (tap → fading ✅ → tap) replaces the Skip/Hint press-and-hold
  popovers and drives the add-friend confirm.
- Fix the move-history "jump": the slid board is inert and the stage can't
  scroll, so a swipe up genuinely closes the history.

Remove Menu.svelte + HoldConfirm.svelte. Docs: UI_DESIGN, FUNCTIONAL(+ru),
PRERELEASE. UI check/unit/build/bundle/e2e (Chromium+WebKit) all green.

ui/src/game/CommsHub.svelte

@@ -0,0 +1,51 @@
+<script lang="ts">
+  import Screen from '../components/Screen.svelte';
+  import TabBar from '../components/TabBar.svelte';
+  import ChatScreen from './ChatScreen.svelte';
+  import CheckScreen from './CheckScreen.svelte';
+  import { t } from '../lib/i18n/index.svelte';
+  import { getCachedGame } from '../lib/gamecache';
+
+  // The in-game comms hub: a single nav bar + bottom tab bar hosting Chat and the word
+  // Dictionary. Tabs switch in place, so the back control always returns to the game. The
+  // Dictionary tab is offered only while the game is active (mirrors the old "check word").
+  type CommsTab = 'chat' | 'dictionary';
+  let { id, initialTab = 'chat' }: { id: string; initialTab?: CommsTab } = $props();
+
+  // The game is rendered (and cached) before its comms open, so the cache tells us whether
+  // it is still active without another fetch; an unknown game keeps the Dictionary offered.
+  const active = $derived(getCachedGame(id)?.view.game.status !== 'finished');
+  // Seeded once from the entry route's tab and then owned locally; the effect below
+  // corrects a Dictionary deep-link into a finished game back to Chat.
+  // svelte-ignore state_referenced_locally
+  let tab = $state<CommsTab>(initialTab);
+  $effect(() => {
+    if (tab === 'dictionary' && !active) tab = 'chat';
+  });
+</script>
+
+<Screen
+  title={t(tab === 'chat' ? 'game.chat' : 'game.checkWord')}
+  back={`/game/${id}`}
+  scroll={tab === 'dictionary'}
+  column={tab === 'chat'}
+>
+  {#if tab === 'chat'}
+    <ChatScreen {id} />
+  {:else}
+    <CheckScreen {id} />
+  {/if}
+
+  {#snippet tabbar()}
+    <TabBar>
+      <button class="tab" class:active={tab === 'chat'} onclick={() => (tab = 'chat')} aria-label={t('game.chat')}>
+        <span class="sq">💬</span>
+      </button>
+      {#if active}
+        <button class="tab" class:active={tab === 'dictionary'} onclick={() => (tab = 'dictionary')} aria-label={t('game.checkWord')}>
+          <span class="sq">🔎</span>
+        </button>
+      {/if}
+    </TabBar>
+  {/snippet}
+</Screen>