Stage 7 polish: app shell + nav + lobby + settings (Parts A/B/C)

- Screen.svelte shell: nav bar grows, ad+content+tabbar pinned bottom (mobile feel)
- AdBanner.svelte + banner.ts rotator (params, mock long/short, linkify); Header CSS chevron + grow; Menu (bigger CSS hamburger); TabBar + HoldConfirm shared components; user-select:none
- Lobby: hide-empty sections, tab order New/Tournaments/Stats, place-based result badges (result.ts)
- Settings: Board style > Labels (beginner/classic/none) + prefs plumbing (boardlabels.ts); i18n keys + ru mirror

ui/src/components/TabBar.svelte

@@ -0,0 +1,62 @@
+<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.
+  let { children }: { children?: Snippet } = $props();
+</script>
+
+<div class="tabbar">{@render children?.()}</div>
+
+<style>
+  .tabbar {
+    display: flex;
+    gap: 12px;
+    padding: 8px var(--pad);
+    background: var(--bg-elev);
+    border-top: 1px solid var(--border);
+    user-select: none;
+    -webkit-user-select: none;
+  }
+  :global(.tabbar > *) {
+    flex: 1 1 0;
+    min-width: 0;
+  }
+  /* Tab face: an icon square (the press-highlight target) + a tiny truncated label. */
+  :global(.tab) {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    gap: 2px;
+    background: none;
+    border: none;
+    padding: 2px 0;
+    color: var(--text);
+    width: 100%;
+    user-select: none;
+    -webkit-user-select: none;
+  }
+  :global(.tab:disabled) {
+    opacity: 0.4;
+  }
+  :global(.tab .sq) {
+    width: 48px;
+    height: 40px;
+    display: grid;
+    place-items: center;
+    border-radius: 12px;
+    font-size: 1.5rem;
+    line-height: 1;
+    transition: background-color 0.12s;
+  }
+  :global(.tab:active:not(:disabled) .sq) {
+    background: var(--surface-2);
+  }
+  :global(.tab .lbl) {
+    font-size: 0.62rem;
+    color: var(--text-muted);
+    max-width: 100%;
+    white-space: nowrap;
+    overflow: hidden;
+    text-overflow: ellipsis;
+  }
+</style>