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

packages/frontend/src/components/MkAntennaEditor.vue

@@ -4,7 +4,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 -->
 
 <template>
-<MkSpacer :contentMax="700">
+<div class="_spacer" style="--MI_SPACER-w: 700px;">
 	<div>
 		<div class="_gaps_m">
 			<MkInput v-model="name">
@@ -48,7 +48,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 			</div>
 		</div>
 	</div>
-</MkSpacer>
+</div>
 </template>
 
 <script lang="ts" setup>