fix: validation (better #8456) (#8461)

* Revert "revert 484e023c0"

This reverts commit c03b70c949.

* also allow pure renote

* fix checks for pure renote

packages/backend/src/server/api/endpoints/users/search-by-username-and-host.ts

@@ -28,7 +28,10 @@ export const paramDef = {
 		limit: { type: 'integer', minimum: 1, maximum: 100, default: 10 },
 		detail: { type: 'boolean', default: true },
 	},
-	required: [],
+	anyOf: [
+		{ required: ['username'] },
+		{ required: ['host'] },
+	],
 } as const;
 
 // TODO: avatar,bannerをJOINしたいけどエラーになる