Default UI redesign (#7429)

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* Update default.sidebar.vue

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* Update sticky-sidebar.ts

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* Update messaging-room.form.vue

* Update timeline.vue

src/client/ui/chat/side.vue

@@ -117,7 +117,7 @@ export default defineComponent({
 .mrajymqm {
 	$header-height: 54px; // TODO: どこかに集約したい
 
-	--section-padding: 16px;
+	--root-margin: 16px;
 	--margin: var(--marginHalf);
 
 	height: 100%;
@@ -137,7 +137,7 @@ export default defineComponent({
 		-webkit-backdrop-filter: blur(32px);
 		backdrop-filter: blur(32px);
 		background-color: var(--header);
-		border-bottom: solid 1px var(--divider);
+		border-bottom: solid 0.5px var(--divider);
 		box-sizing: border-box;
 
 		> ._button {