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/ChatScreen.svelte

@@ -1,15 +1,14 @@
 <script lang="ts">
   import { onMount } from 'svelte';
-  import Screen from '../components/Screen.svelte';
   import Chat from './Chat.svelte';
   import { gateway } from '../lib/gateway';
   import { app, handleError, clearChatUnread } from '../lib/app.svelte';
-  import { t } from '../lib/i18n/index.svelte';
   import type { ChatMessage, StateView } from '../lib/model';
 
-  // The chat is its own screen, so the soft keyboard simply resizes the viewport with
-  // the input pinned to the bottom — no modal relayout jank. It loads the game state (for the
-  // turn-based chat/nudge toggle) and the message list, and clears the unread badge while open.
+  // The Chat tab body, hosted by CommsHub (which supplies the nav bar + tab bar). The
+  // hub lays it out as a non-scrolling column, so the soft keyboard simply resizes the
+  // viewport with the input pinned to the bottom. It loads the game state (for the
+  // turn-based chat/nudge toggle) and the message list, and clears the unread while open.
   let { id }: { id: string } = $props();
 
   let view = $state<StateView | null>(null);
@@ -88,6 +87,4 @@
   }
 </script>
 
-<Screen title={t('game.chat')} back={`/game/${id}`} scroll={false} column>
-  <Chat {messages} {myId} {busy} myTurn={isMyTurn} {nudgeOnCooldown} onsend={sendChat} onnudge={nudge} />
-</Screen>
+<Chat {messages} {myId} {busy} myTurn={isMyTurn} {nudgeOnCooldown} onsend={sendChat} onnudge={nudge} />