Add style to flush

packages/backend/src/server/web/views/flush.pug

@@ -1,7 +1,28 @@
 doctype html
 
 html
-	#msg
+
+	head
+		meta(charset='utf-8')
+		meta(name='application-name' content='Misskey')
+		title Misskey Repair Tool
+		style.
+			* {
+				font-family: BIZ UDGothic, Roboto, HelveticaNeue, Arial, sans-serif;
+				font-size: 16px;
+				color: #dfddcc;
+			}
+
+			body,
+			html {
+				background-color: #222;
+				justify-content: center;
+				margin: auto;
+				width: 80%;
+				padding: 10px;
+				text-align: center;
+			}
+
 		script.
 			const msg = document.getElementById('msg');
 			const successText = `\nSuccess Flush! <a href="/">Back to Misskey</a>\n成功しました。<a href="/">Misskeyを開き直してください。</a>`;
@@ -45,3 +66,6 @@ html
 			function message(text) {
 				msg.insertAdjacentHTML('beforeend', `<p>[${(new Date()).toString()}] ${text.replace(/\n/g,'<br>')}</p>`)
 			}
+
+	body
+		#msg