perf(assets): Player/Admin 静态图改用 WebP，vs 保留 PNG

Player 端 banner/bg/card/h5bg 等改为 webp 并移除旧 png；Admin 登录背景改 webp；vs 对阵图仍用 png。

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/player/src/views/RegisterView.vue

@@ -8,7 +8,7 @@ import { useAppLocale } from '../composables/useAppLocale';
 import { useSmsCode } from '../composables/useSmsCode';
 import LocaleSwitcher from '../components/LocaleSwitcher.vue';
 import PhoneCountrySelect from '../components/PhoneCountrySelect.vue';
-import loginBg from '../assets/images/h5bg.png';
+import loginBg from '../assets/images/h5bg.webp';
 
 const { t, locale } = useI18n();
 const { initFromUser } = useAppLocale();