enhance(frontend): ナビゲーションバーの副ボタンを非表示にできるように

packages/frontend/src/ui/_common_/navbar.vue

@@ -65,7 +65,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 	</svg>
 	-->
 
-	<div v-if="!forceIconOnly" :class="$style.subButtons">
+	<div v-if="!forceIconOnly && prefer.r.showNavbarSubButtons.value" :class="$style.subButtons">
 		<div :class="[$style.subButton, $style.menuEditButton]">
 			<svg viewBox="0 0 16 64" :class="$style.subButtonShape">
 				<g transform="matrix(0.333333,0,0,0.222222,0.000895785,21.3333)">