enhance(frontend): viewportの属性を起動後に変化させないことにより処理を簡略化+安定性向上

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

@@ -28,7 +28,7 @@ html
 		meta(name='theme-color-orig' content= themeColor || '#86b300')
 		meta(property='og:site_name' content= instanceName || 'Misskey')
 		meta(property='instance_url' content= instanceUrl)
-		meta(name='viewport' content='width=device-width, initial-scale=1')
+		meta(name='viewport' content='width=device-width, initial-scale=1, minimum-scale=1, maximum-scale=1, user-scalable=no, viewport-fit=cover')
 		meta(name='format-detection' content='telephone=no,date=no,address=no,email=no,url=no')
 		link(rel='icon' href= icon || '/favicon.ico')
 		link(rel='apple-touch-icon' href= appleTouchIcon || '/apple-touch-icon.png')

packages/frontend/src/boot/common.ts

@@ -109,13 +109,6 @@ export async function common(createVue: () => Promise<App<Element>>) {
 		else window.location.reload();
 	});
 
-	// If mobile, insert the viewport meta tag
-	if (['smartphone', 'tablet'].includes(deviceKind)) {
-		const viewport = window.document.getElementsByName('viewport').item(0);
-		viewport.setAttribute('content',
-			`${viewport.getAttribute('content')}, minimum-scale=1, maximum-scale=1, user-scalable=no, viewport-fit=cover`);
-	}
-
 	//#region Set lang attr
 	const html = window.document.documentElement;
 	html.setAttribute('lang', lang);