refactor: standardize code formatting across components and utilities

- Updated formatting in SiteFooter and SiteHeader components for consistency.
- Refactored Badge, Button, Card, Separator components to improve readability.
- Enhanced markdown parsing logic in announcements and markdown utility functions.
- Adjusted ESLint configuration for better code quality checks.
- Added biome.json for BiomeJS configuration.
- Updated package.json and configuration files for improved dependency management.

app/announcements/loading.tsx

@@ -1,10 +1,10 @@
 export default function AnnouncementsLoading() {
-  return (
-    <div className="mx-auto flex w-full max-w-5xl flex-1 items-center justify-center px-4 py-12 sm:px-8">
-      <div className="flex items-center gap-3 rounded-xl border bg-card px-5 py-3 text-sm text-muted-foreground shadow-sm">
-        <span className="inline-block size-2.5 animate-pulse rounded-full bg-primary" />
-        お知らせを読み込み中...
-      </div>
-    </div>
-  );
+	return (
+		<div className="mx-auto flex w-full max-w-5xl flex-1 items-center justify-center px-4 py-12 sm:px-8">
+			<div className="flex items-center gap-3 rounded-xl border bg-card px-5 py-3 text-sm text-muted-foreground shadow-sm">
+				<span className="inline-block size-2.5 animate-pulse rounded-full bg-primary" />
+				お知らせを読み込み中...
+			</div>
+		</div>
+	);
 }