perf(frontend): use css-native implementation for spacer rather than vue component

packages/frontend/src/pages/scratchpad.vue

@@ -5,7 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 
 <template>
 <PageWithHeader>
-	<MkSpacer :contentMax="800">
+	<div class="_spacer" style="--MI_SPACER-w: 800px;">
 		<div :class="$style.root">
 			<div class="_gaps_s">
 				<div :class="$style.editor" class="_panel">
@@ -50,7 +50,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 				{{ i18n.ts.scratchpadDescription }}
 			</div>
 		</div>
-	</MkSpacer>
+	</div>
 </PageWithHeader>
 </template>