feat(ui): lobby invitation card redesign + new-game tweaks

- Lobby friend-invitation card: icon-only checkmark/cross actions stacked in a
  min-width right column; the middle column (From <name> + flag + variant rules,
  like New Game) grows and wraps. The cross now opens a decline-confirmation modal
  (mirroring the in-game resign confirm) instead of declining on first tap.
- New Game with a friend: a lone offered variant is pre-selected and its picker
  disabled (nothing else to choose); relabel 'Тип игры' -> 'Вариант' and
  'Подсказок на игрока' -> 'Подсказки'.
- Quick game: pin the Start button to the bottom of the screen, mirroring the
  friend-game Send-invitation button.

ui/src/screens/NewGame.svelte

@@ -67,9 +67,12 @@
   let friends = $state<AccountRef[]>([]);
   let selected = $state<string[]>([]);
   let friendFilter = $state('');
-  // No default game type yet — the player must pick one (a smarter default from play
-  // history / language would be a future refinement). '' renders the disabled placeholder option.
+  // A lone offered variant is pre-selected and its picker disabled (nothing else to choose);
+  // with several, the player picks. '' renders the disabled placeholder option.
   let inviteVariant = $state<Variant | ''>('');
+  $effect(() => {
+    if (variants.length === 1 && !inviteVariant) inviteVariant = variants[0].id;
+  });
   let timeoutSecs = $state(86400);
   let hints = $state(1);
 
@@ -152,6 +155,7 @@
             <input type="checkbox" bind:checked={multipleWords} />
           </label>
         {/if}
+        <div class="grow"></div>
         <p class="movelimit">{opponent === 'ai' ? t('new.aiInactiveLimit') : t('new.moveLimit', { n: AUTO_MATCH_HOURS })}</p>
         {#if opponent === 'random'}<p class="searchhint">{t('new.searchHint')}</p>{/if}
         <button
@@ -179,7 +183,7 @@
           <div class="settings-row">
             <label class="field">
               <span>{t('new.gameType')}</span>
-              <select bind:value={inviteVariant} class:placeholder={!inviteVariant}>
+              <select bind:value={inviteVariant} class:placeholder={!inviteVariant} disabled={variants.length === 1}>
                 <option value="" disabled>—</option>
                 {#each variants as v (v.id)}<option value={v.id}>{t(v.label)}</option>{/each}
               </select>
@@ -387,6 +391,11 @@
     color: var(--text-muted);
     margin: 0;
   }
+  /* Pushes the auto-match start cluster (move-limit hint + Start button) to the bottom,
+     mirroring the friend-game invite button pinned by the .fg scroll area. */
+  .grow {
+    flex: 1;
+  }
   .invite {
     flex: 0 0 auto;
     padding: 14px;