Landing v2: icon switchers, ephemeral theme, channel link, drop browser CTA

Owner review-pass rework of the landing page:
- Rename the per-language Telegram link build var
  VITE_TELEGRAM_LINK_EN/_RU -> VITE_TELEGRAM_GAME_CHANNEL_NAME_EN/_RU
  (it carries a channel username; the landing builds https://t.me/<name> --
  the same channels the connector posts to via TELEGRAM_GAME_CHANNEL_ID_*).
- Language switcher -> a globe icon dropdown (flags + names), saved + synced
  to the app prefs.
- Theme switcher -> a sun/moon icon toggle, ephemeral (follows the system
  scheme, no auto, never persisted) -- galaxy-game style.
- Drop the "Play in browser" CTA (no standalone-web onboarding yet).

Docs: FUNCTIONAL(+ru), PLAN, deploy + ui READMEs.

ui/src/Landing.svelte

@@ -1,89 +1,84 @@
 <script lang="ts">
   import { onMount } from 'svelte';
-  import { applyReduceMotion, applyTheme, type ThemePref } from './lib/theme';
-  import { i18n, localeFrom, setLocale, t, type Locale, type MessageKey } from './lib/i18n/index.svelte';
+  import { applyTheme } from './lib/theme';
+  import { i18n, localeFrom, setLocale, t, type Locale } from './lib/i18n/index.svelte';
   import { loadPrefs, savePrefs, type Prefs } from './lib/session';
   import { aboutContent } from './lib/aboutContent';
-  import { telegramBotLink } from './lib/landing';
+  import { telegramChannelLink } from './lib/landing';
 
-  // Standalone landing page (Stage 17): the public entry at "/", separate from the game SPA
-  // (served at /app/ and /telegram/). It reuses the app's theme/i18n/prefs leaf modules — but
-  // not the app store — so it stays light (no gateway, auth or live stream).
+  // Standalone landing page (Stage 17), the public entry at "/" (the game SPA lives at /app/ and
+  // /telegram/). It reuses the app's theme/i18n/prefs leaf modules — not the app store — so it
+  // stays light. Theme is EPHEMERAL here (no auto, no persistence): it starts from the system
+  // scheme and the icon toggles light<->dark in memory. Language IS persisted (synced with the app).
 
-  const themes: ThemePref[] = ['auto', 'light', 'dark'];
-  const themeLabel: Record<ThemePref, MessageKey> = {
-    auto: 'settings.themeAuto',
-    light: 'settings.themeLight',
-    dark: 'settings.themeDark',
-  };
-  const locales: Locale[] = ['en', 'ru'];
-
-  let theme = $state<ThemePref>('auto');
+  let theme = $state<'light' | 'dark'>('light');
+  let langOpen = $state(false);
   let prefs: Partial<Prefs> = {};
 
-  // The away/move clock the random-game copy mentions (backend game.DefaultTurnTimeout = 24h).
-  const about = $derived(aboutContent(i18n.locale, 24));
-  const tgLink = $derived(telegramBotLink(i18n.locale));
+  const about = $derived(aboutContent(i18n.locale, 24)); // 24h = the auto-match move clock
+  const tgLink = $derived(telegramChannelLink(i18n.locale));
+  const locales: { code: Locale; label: string }[] = [
+    { code: 'en', label: '🇬🇧 English' },
+    { code: 'ru', label: '🇷🇺 Русский' },
+  ];
+
+  function systemTheme(): 'light' | 'dark' {
+    return typeof matchMedia !== 'undefined' && matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
+  }
 
   onMount(async () => {
     prefs = await loadPrefs();
-    theme = prefs.theme ?? 'auto';
+    theme = systemTheme();
     applyTheme(theme);
-    applyReduceMotion(prefs.reduceMotion ?? false);
     setLocale(prefs.locale ?? localeFrom(typeof navigator !== 'undefined' ? navigator.language : 'en'));
   });
 
-  function persist(): void {
-    // savePrefs takes the full set, so keep the labels/lines the app may have stored.
+  function toggleTheme(): void {
+    theme = theme === 'light' ? 'dark' : 'light';
+    applyTheme(theme); // ephemeral — deliberately not persisted
+  }
+
+  function chooseLocale(lc: Locale): void {
+    setLocale(lc);
+    langOpen = false;
+    // Persist the language only, keeping the app's other prefs (notably its own persisted theme).
     void savePrefs({
-      theme,
-      locale: i18n.locale,
+      theme: prefs.theme ?? 'auto',
+      locale: lc,
       reduceMotion: prefs.reduceMotion ?? false,
       boardLabels: prefs.boardLabels ?? 'beginner',
       boardLines: prefs.boardLines ?? false,
     });
-  }
-  function chooseTheme(th: ThemePref): void {
-    theme = th;
-    applyTheme(th);
-    persist();
-  }
-  function chooseLocale(lc: Locale): void {
-    setLocale(lc);
-    persist();
+    prefs = { ...prefs, locale: lc };
   }
 </script>
 
 <main class="landing">
   <header class="bar">
-    <div class="seg">
-      {#each locales as lc (lc)}
-        <button class="opt" class:active={i18n.locale === lc} onclick={() => chooseLocale(lc)}>
-          {t(lc === 'en' ? 'lang.en' : 'lang.ru')}
-        </button>
-      {/each}
-    </div>
-    <div class="seg">
-      {#each themes as th (th)}
-        <button class="opt" class:active={theme === th} onclick={() => chooseTheme(th)}>
-          {t(themeLabel[th])}
-        </button>
-      {/each}
+    <div class="lang">
+      <button class="icon" aria-label="Language" aria-expanded={langOpen} onclick={() => (langOpen = !langOpen)}>🌐</button>
+      {#if langOpen}
+        <!-- svelte-ignore a11y_consider_explicit_label -->
+        <button class="backdrop" onclick={() => (langOpen = false)}></button>
+        <div class="menu" role="menu">
+          {#each locales as l (l.code)}
+            <button role="menuitem" class:on={i18n.locale === l.code} onclick={() => chooseLocale(l.code)}>{l.label}</button>
+          {/each}
+        </div>
+      {/if}
     </div>
+    <button class="icon" aria-label="Theme" onclick={toggleTheme}>{theme === 'light' ? '☼' : '☾'}</button>
   </header>
 
   <section class="hero">
     <h1>{about.title}</h1>
     <p class="tagline">{t('landing.tagline')}</p>
-    <div class="cta">
-      <a class="play primary" href="/app/">{t('landing.playWeb')}</a>
-      {#if tgLink}
-        <a class="play tg" href={tgLink} target="_blank" rel="noopener noreferrer">
-          <img src="telegram-logo.svg" alt="" width="22" height="22" />
-          {t('landing.playTelegram')}
-        </a>
-      {/if}
-    </div>
+    {#if tgLink}
+      <a class="play" href={tgLink} target="_blank" rel="noopener noreferrer">
+        <img src="telegram-logo.svg" alt="" width="22" height="22" />
+        {t('landing.playTelegram')}
+      </a>
+    {/if}
   </section>
 
   <section class="info">
@@ -125,32 +120,65 @@
   .bar {
     display: flex;
     justify-content: space-between;
-    gap: 10px;
-    flex-wrap: wrap;
+    align-items: center;
   }
-  .seg {
-    display: flex;
-    gap: 6px;
+  .lang {
+    position: relative;
   }
-  .opt {
-    padding: 7px 12px;
-    border: 1px solid var(--border);
-    background: var(--surface);
+  .icon {
+    min-width: 40px;
+    min-height: 40px;
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    font-size: 1.25rem;
+    background: transparent;
     color: var(--text);
+    border: 1px solid var(--border);
     border-radius: var(--radius-sm);
-    user-select: none;
-    font-size: 0.85rem;
+    cursor: pointer;
   }
-  .opt.active {
-    background: var(--accent);
-    color: var(--accent-text);
-    border-color: var(--accent);
+  .backdrop {
+    position: fixed;
+    inset: 0;
+    z-index: 8;
+    background: none;
+    border: none;
+  }
+  .menu {
+    position: absolute;
+    left: 0;
+    top: calc(100% + 6px);
+    z-index: 9;
+    background: var(--surface);
+    border: 1px solid var(--border);
+    border-radius: var(--radius-sm);
+    box-shadow: var(--shadow);
+    display: flex;
+    flex-direction: column;
+    min-width: 150px;
+    overflow: hidden;
+  }
+  .menu button {
+    text-align: left;
+    padding: 10px 14px;
+    background: none;
+    border: none;
+    color: var(--text);
+    white-space: nowrap;
+  }
+  .menu button:hover {
+    background: var(--surface-2);
+  }
+  .menu button.on {
+    color: var(--accent);
+    font-weight: 600;
   }
   .hero {
     text-align: center;
     display: flex;
     flex-direction: column;
-    gap: 14px;
+    gap: 16px;
     padding: 24px 0 8px;
   }
   .hero h1 {
@@ -164,33 +192,20 @@
     color: var(--text-muted);
     font-size: 1.05rem;
   }
-  .cta {
-    display: flex;
-    gap: 12px;
-    justify-content: center;
-    flex-wrap: wrap;
-    margin-top: 6px;
-  }
   .play {
+    align-self: center;
     display: inline-flex;
     align-items: center;
     gap: 9px;
-    padding: 12px 22px;
+    padding: 12px 24px;
     border-radius: var(--radius-sm);
     font-weight: 700;
     text-decoration: none;
-    border: 1px solid var(--border);
-  }
-  .play.primary {
     background: var(--accent);
     color: var(--accent-text);
-    border-color: var(--accent);
+    margin-top: 6px;
   }
-  .play.tg {
-    background: var(--surface);
-    color: var(--text);
-  }
-  .play.tg img {
+  .play img {
     display: block;
   }
   .info {
@@ -225,7 +240,6 @@
     display: flex;
     flex-direction: column;
     gap: 5px;
-    color: var(--text);
   }
   .ft {
     margin-top: auto;