feat: 接入玩家入口与API代理

- 新增 /api 重写代理，支持 LOTTERY_API_PROXY_TARGET 配置
- 玩家首页切换为 EntryGate，并移除 layout 对 PlayerAppShell 的包裹
- 请求层拆分语言头与玩家鉴权注入逻辑，引入 zustand 依赖
- 允许提交 .env.example 供本地配置参考

src/lib/lottery-locale.ts

@@ -0,0 +1,57 @@
+import { AxiosHeaders, type AxiosRequestConfig } from "axios";
+
+type LotteryLocale = "zh" | "en" | "ne";
+
+let overrideLocale: LotteryLocale | null = null;
+
+export function setLotteryRequestLocale(locale: string | null): void {
+  if (locale === null) {
+    overrideLocale = null;
+    return;
+  }
+  const p = locale.trim().toLowerCase().split("-")[0] ?? "";
+  overrideLocale = isLotteryLocale(p) ? p : null;
+}
+
+function isLotteryLocale(value: string): value is LotteryLocale {
+  return value === "zh" || value === "en" || value === "ne";
+}
+
+function requestLocale(): LotteryLocale {
+  if (overrideLocale) {
+    return overrideLocale;
+  }
+  if (typeof document !== "undefined") {
+    const tag = document.documentElement.lang.trim().toLowerCase();
+    const primary = tag.split("-")[0] ?? tag;
+    if (isLotteryLocale(primary)) {
+      return primary;
+    }
+  }
+  return "en";
+}
+
+function acceptLanguage(loc: LotteryLocale): string {
+  if (loc === "zh") {
+    return "zh-CN,zh;q=0.9,en;q=0.8";
+  }
+  if (loc === "ne") {
+    return "ne,ne-NP;q=0.9,en;q=0.8";
+  }
+  return "en-US,en;q=0.9";
+}
+
+export function withLotteryLocaleHeaders(
+  config: AxiosRequestConfig,
+): AxiosRequestConfig {
+  const loc = requestLocale();
+  const merged: AxiosRequestConfig = { ...config };
+  // Axios 的 RequestConfig.headers 类型比 concat 能接受的头对象更窄
+  const headers = AxiosHeaders.concat(
+    merged.headers as Parameters<typeof AxiosHeaders.concat>[0],
+  );
+  headers.set("X-Locale", loc);
+  headers.set("Accept-Language", acceptLanguage(loc));
+  merged.headers = headers;
+  return merged;
+}