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/components/TabBar.svelte

@@ -1,7 +1,7 @@
 <script lang="ts">
   import type { Snippet } from 'svelte';
   // The bottom tab bar: square borderless buttons, evenly distributed, mobile-OS feel.
-  // Direct children (plain `.tab` buttons or HoldConfirm wrappers) share the width.
+  // Direct children (plain `.tab` buttons or TapConfirm wrappers) share the width.
   let { children }: { children?: Snippet } = $props();
 </script>
 
@@ -53,6 +53,29 @@
   :global(.tab:active:not(:disabled) .sq) {
     background: var(--surface-2);
   }
+  /* A tab that navigates between peer views (Settings / Comms hubs) stays highlighted
+     while selected: a filled square with an accent underline, distinct from the
+     momentary press tint above. */
+  :global(.tab.active .sq) {
+    background: var(--surface-2);
+    box-shadow: inset 0 -2px 0 var(--accent);
+  }
+  /* A small count badge on the icon square's corner (lobby ⚙️, the Friends tab, the
+     hint count) — one shared style so every tab badge reads the same. */
+  :global(.tab .badge) {
+    position: absolute;
+    top: -3px;
+    right: -3px;
+    font-size: 0.68rem;
+    font-weight: 700;
+    background: var(--accent);
+    color: var(--accent-text);
+    border-radius: 999px;
+    min-width: 15px;
+    padding: 0 3px;
+    line-height: 1.4;
+    text-align: center;
+  }
   :global(.tab .lbl) {
     font-size: 0.62rem;
     color: var(--text-muted);