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/HoldConfirm.svelte

@@ -0,0 +1,102 @@
+<script lang="ts">
+  import type { Snippet } from 'svelte';
+  // A press-and-hold control: a short tap opens a popover (the consumer renders its
+  // buttons), a ~holdMs hold runs `onhold` immediately. Reused by MakeMove and the
+  // game tab-bar confirmations. The popover snippet receives a `close` callback.
+  let {
+    onhold,
+    holdMs = 700,
+    disabled = false,
+    triggerClass = '',
+    trigger,
+    popover,
+  }: {
+    onhold: () => void;
+    holdMs?: number;
+    disabled?: boolean;
+    triggerClass?: string;
+    trigger: Snippet;
+    popover: Snippet<[() => void]>;
+  } = $props();
+
+  let open = $state(false);
+  let timer: ReturnType<typeof setTimeout> | null = null;
+  let held = false;
+
+  function clear() {
+    if (timer) {
+      clearTimeout(timer);
+      timer = null;
+    }
+  }
+  function down() {
+    if (disabled) return;
+    held = false;
+    clear();
+    timer = setTimeout(() => {
+      held = true;
+      open = false;
+      onhold();
+    }, holdMs);
+  }
+  function up() {
+    clear();
+    if (!held && !disabled) open = true;
+  }
+  function leave() {
+    clear();
+  }
+  const close = () => (open = false);
+</script>
+
+<div class="hc">
+  <button
+    class="trigger {triggerClass}"
+    {disabled}
+    onpointerdown={down}
+    onpointerup={up}
+    onpointerleave={leave}
+    onpointercancel={leave}
+  >
+    {@render trigger()}
+  </button>
+
+  {#if open}
+    <!-- svelte-ignore a11y_click_events_have_key_events -->
+    <!-- svelte-ignore a11y_no_static_element_interactions -->
+    <div class="backdrop" onclick={close}></div>
+    <div class="popover">{@render popover(close)}</div>
+  {/if}
+</div>
+
+<style>
+  .hc {
+    position: relative;
+    display: flex;
+  }
+  .trigger {
+    width: 100%;
+    background: none;
+    border: none;
+    padding: 0;
+    color: inherit;
+    touch-action: none;
+    user-select: none;
+    -webkit-user-select: none;
+  }
+  .backdrop {
+    position: fixed;
+    inset: 0;
+    z-index: 18;
+  }
+  .popover {
+    position: absolute;
+    bottom: calc(100% + 6px);
+    left: 50%;
+    transform: translateX(-50%);
+    z-index: 19;
+    display: flex;
+    gap: 4px;
+    white-space: nowrap;
+  }
+</style>