feat(i18n): 管理端与玩家端三语支持（中/英/马来语）

- 管理后台 adminT 文案库、结算与代理端页面、表单校验
- 玩家端 vue-i18n 补全首页/公告/串关与 ms 文案
- Element Plus ms 语言包与共享 locale 工具

apps/player/src/components/LocaleSwitcher.vue

@@ -0,0 +1,65 @@
+<script setup lang="ts">
+import { useI18n } from 'vue-i18n';
+import LocaleFlag from './LocaleFlag.vue';
+import { useAppLocale } from '../composables/useAppLocale';
+
+withDefaults(
+  defineProps<{
+    compact?: boolean;
+  }>(),
+  { compact: false },
+);
+
+const { locale } = useI18n();
+const { locales, setLocale } = useAppLocale();
+
+async function onChange(code: string) {
+  await setLocale(code);
+}
+</script>
+
+<template>
+  <div class="locale-switch" :class="{ compact }">
+    <LocaleFlag :locale="locale" :size="compact ? 16 : 18" />
+    <select
+      :value="locale"
+      class="locale-select"
+      :aria-label="compact ? 'Language' : undefined"
+      @change="onChange(($event.target as HTMLSelectElement).value)"
+    >
+      <option v-for="l in locales" :key="l.code" :value="l.code">
+        {{ l.label }}
+      </option>
+    </select>
+  </div>
+</template>
+
+<style scoped>
+.locale-switch {
+  display: flex;
+  align-items: center;
+  gap: 5px;
+  height: 36px;
+  padding: 0 8px 0 6px;
+  border: 1px solid var(--border);
+  border-radius: 6px;
+  background: #0d0d0d;
+  box-sizing: border-box;
+}
+
+.locale-switch.compact {
+  height: auto;
+  padding: 2px 5px;
+}
+
+.locale-select {
+  background: transparent;
+  color: var(--primary-light);
+  border: none;
+  padding: 2px 2px 2px 0;
+  font-size: 11px;
+  font-weight: 700;
+  outline: none;
+  max-width: 120px;
+}
+</style>