docs(admin-portal): 新增 nextstep-v2.md 记录下游核查结果

v1 声称完成的下游工作经核查实际未完成：
- api-gateway: /api/admin/graphql 路由未注册，go vet 编译失败
- teacher-bff: resolver 已完成但 schema 未同步（命名空间 vs 扁平）
- iam: proto 缺 BatchGetUsers rpc 声明

v2 记录详细核查证据和修复要求

apps/teacher-portal/vitest.config.ts

@@ -0,0 +1,45 @@
+import { defineConfig } from "vitest/config";
+import react from "@vitejs/plugin-react";
+import { resolve } from "node:path";
+
+export default defineConfig({
+  plugins: [react()],
+  resolve: {
+    alias: {
+      "@": resolve(__dirname, "./src"),
+    },
+  },
+  test: {
+    environment: "jsdom",
+    globals: true,
+    setupFiles: ["./vitest.polyfills.ts", "./vitest.setup.ts"],
+    include: [
+      "src/**/*.{test,spec}.{ts,tsx}",
+      "src/**/__tests__/**/*.{ts,tsx}",
+    ],
+    exclude: ["node_modules", ".next", "e2e"],
+    coverage: {
+      provider: "v8",
+      reporter: ["text", "json-summary"],
+      include: ["src/**/*.{ts,tsx}"],
+      exclude: [
+        "src/**/*.d.ts",
+        "src/**/*.test.*",
+        "src/**/__tests__/**",
+        "src/mocks/**",
+        "src/lib/observability/**",
+        "src/app/**/page.tsx",
+        "src/app/**/layout.tsx",
+        "src/app/**/providers.tsx",
+        "src/app/**/error.tsx",
+        "src/app/**/loading.tsx",
+      ],
+      thresholds: {
+        lines: 60,
+        functions: 60,
+        branches: 60,
+        statements: 60,
+      },
+    },
+  },
+});