新增 build:test 方便构建线上的测试环境，优化分享码功能的交互

vite.legacy.config.ts

@@ -43,12 +43,19 @@ function legacySkipModernCssPlugin(): Plugin {
   };
 }
 
+/* ── Deploy base path ── */
+const DEPLOY_ENV = process.env.DEPLOY_ENV || "production";
+const isProd = process.env.NODE_ENV === "production";
+const deployBase = isProd
+  ? (DEPLOY_ENV === "test" ? "/x9/test/legacy/" : "/x9/v2/legacy/")
+  : "/";
+
 export default defineConfig({
   plugins: [legacySkipModernCssPlugin(), legacyIndexRewritePlugin(), react(), jsxLocPlugin()],
   define: {
     "import.meta.env.VITE_X9_LEGACY": JSON.stringify("1"),
   },
-  base: process.env.NODE_ENV === "production" ? "/x9/v2/legacy/" : "/",
+  base: deployBase,
   resolve: {
     alias: {
       "@": path.resolve(PROJECT_ROOT, "client", "src"),