fix: restore flex layout on #game-content wrapper

The SSE patching refactor (0808c4d) wrapped game elements in a bare
<div id="game-content"> without propagating the flex classes from
<main>. This broke center-alignment and vertical spacing for both
Connect 4 and Snake game pages.

features/snakegame/pages/game.templ

@@ -43,7 +43,7 @@ templ GamePage(sg *snake.SnakeGame, mySlot int, messages []chat.Message, chatCfg
 }
 
 templ GameContent(sg *snake.SnakeGame, mySlot int, messages []chat.Message, chatCfg chatcomponents.Config, gameID string) {
-	<div id="game-content">
+	<div id="game-content" class="flex flex-col items-center gap-4">
 		@components.LiveClock()
 		@components.BackToLobby()
 		<h1 class="text-3xl font-bold">~~~~</h1>