refactoring

Resolve #7779

packages/backend/src/misc/normalize-for-search.ts

@@ -0,0 +1,6 @@
+export function normalizeForSearch(tag: string): string {
+	// ref.
+	// - https://analytics-note.xyz/programming/unicode-normalization-forms/
+	// - https://maku77.github.io/js/string/normalize.html
+	return tag.normalize('NFKC').toLowerCase();
+}