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

packages/frontend/src/pages/user/flashs.vue

@@ -4,11 +4,11 @@ SPDX-License-Identifier: AGPL-3.0-only
 -->
 
 <template>
-<MkSpacer :contentMax="700">
+<div class="_spacer" style="--MI_SPACER-w: 700px;">
 	<MkPagination v-slot="{items}" ref="list" :pagination="pagination">
 		<MkFlashPreview v-for="flash in items" :key="flash.id" :flash="flash" class="_margin"/>
 	</MkPagination>
-</MkSpacer>
+</div>
 </template>
 
 <script lang="ts" setup>