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/screens/About.svelte

@@ -1,5 +1,4 @@
 <script lang="ts">
-  import Screen from '../components/Screen.svelte';
   import { t } from '../lib/i18n/index.svelte';
   import { app } from '../lib/app.svelte';
   import { aboutContent } from '../lib/aboutContent';
@@ -10,31 +9,29 @@
   const c = $derived(aboutContent(app.locale, AUTO_MATCH_HOURS));
 </script>
 
-<Screen title={t('about.title')} back="/">
-  <div class="page">
-    <h1>{c.title}</h1>
-    <p>
-      {c.rulesPrefix}<a href={c.rulesUrl} target="_blank" rel="noopener noreferrer">{c.rulesLink}</a>.
-    </p>
+<div class="page">
+  <h1>{c.title}</h1>
+  <p>
+    {c.rulesPrefix}<a href={c.rulesUrl} target="_blank" rel="noopener noreferrer">{c.rulesLink}</a>.
+  </p>
 
-    <section>
-      <h2>{c.randomTitle}</h2>
-      <p class="respect">❗️{c.randomRespect}</p>
-      <ul>
-        {#each c.random as item (item)}<li>{item}</li>{/each}
-      </ul>
-    </section>
+  <section>
+    <h2>{c.randomTitle}</h2>
+    <p class="respect">❗️{c.randomRespect}</p>
+    <ul>
+      {#each c.random as item (item)}<li>{item}</li>{/each}
+    </ul>
+  </section>
 
-    <section>
-      <h2>{c.friendsTitle}</h2>
-      <ul>
-        {#each c.friends as item (item)}<li>{item}</li>{/each}
-      </ul>
-    </section>
+  <section>
+    <h2>{c.friendsTitle}</h2>
+    <ul>
+      {#each c.friends as item (item)}<li>{item}</li>{/each}
+    </ul>
+  </section>
 
-    <p class="muted">{t('about.version', { v: version })}</p>
-  </div>
-</Screen>
+  <p class="muted">{t('about.version', { v: version })}</p>
+</div>
 
 <style>
   .page {