feat(client): 初始化前端壳与鉴权守卫（P1-5）

- 技术栈：React 18 + TypeScript + Vite + Tailwind

- API 层：ApiError + 401 自动刷新 + single-flight 重试

- 鉴权：内存 Access Token + Cookie Refresh + 启动 bootstrap

- RBAC：权限映射 + RequireAuth/RequirePermission 路由守卫

- 布局：OA 工作台壳层 + 侧边栏 + 5 个占位页面

- 样式：复用 hyb-web 视觉 token（单向同步）

- 文档：新增 client README，补充 server 联调说明

client/src/pages/LoginPage.tsx

@@ -0,0 +1,96 @@
+import { useState } from "react";
+import { useNavigate, useSearchParams } from "react-router-dom";
+import { isApiError } from "../api/types";
+import { useAuth } from "../auth/AuthContext";
+
+function resolveRedirect(searchParams: URLSearchParams) {
+  const redirect = searchParams.get("redirect");
+  if (!redirect) {
+    return "/dashboard";
+  }
+
+  if (!redirect.startsWith("/")) {
+    return "/dashboard";
+  }
+
+  return redirect;
+}
+
+export function LoginPage() {
+  const navigate = useNavigate();
+  const [searchParams] = useSearchParams();
+  const { login } = useAuth();
+
+  const [identifier, setIdentifier] = useState("[email protected]");
+  const [password, setPassword] = useState("EmployeePassword1234");
+  const [submitting, setSubmitting] = useState(false);
+  const [error, setError] = useState("");
+
+  const redirectTo = resolveRedirect(searchParams);
+
+  async function handleSubmit(event: React.FormEvent<HTMLFormElement>) {
+    event.preventDefault();
+    setSubmitting(true);
+    setError("");
+
+    try {
+      await login(identifier.trim(), password);
+      navigate(redirectTo, { replace: true });
+    } catch (err) {
+      if (isApiError(err)) {
+        setError(`${err.code}: ${err.message}`);
+      } else {
+        setError("登录失败，请稍后重试");
+      }
+    } finally {
+      setSubmitting(false);
+    }
+  }
+
+  return (
+    <div className="card-std border-primary-100">
+      <div className="mb-6">
+        <p className="text-xs font-semibold uppercase tracking-wide text-primary">hyb-oa</p>
+        <h1 className="mt-2 text-2xl font-bold text-slate-900">登录工作台</h1>
+        <p className="mt-2 text-sm text-secondary">使用邮箱/手机号与密码登录。</p>
+      </div>
+
+      <form className="space-y-4" onSubmit={handleSubmit}>
+        <label className="block text-sm font-medium text-slate-700" htmlFor="identifier">
+          账号
+          <input
+            autoComplete="username"
+            className="mt-1 w-full rounded-lg border border-slate-300 bg-white px-3 py-2 text-sm focus:border-primary-400 focus:outline-none focus:ring-2 focus:ring-primary-100"
+            id="identifier"
+            onChange={(event) => setIdentifier(event.target.value)}
+            placeholder="邮箱或手机号"
+            value={identifier}
+          />
+        </label>
+
+        <label className="block text-sm font-medium text-slate-700" htmlFor="password">
+          密码
+          <input
+            autoComplete="current-password"
+            className="mt-1 w-full rounded-lg border border-slate-300 bg-white px-3 py-2 text-sm focus:border-primary-400 focus:outline-none focus:ring-2 focus:ring-primary-100"
+            id="password"
+            onChange={(event) => setPassword(event.target.value)}
+            placeholder="请输入密码"
+            type="password"
+            value={password}
+          />
+        </label>
+
+        {error ? (
+          <p className="rounded-lg border border-red-200 bg-red-50 px-3 py-2 text-sm text-red-600">
+            {error}
+          </p>
+        ) : null}
+
+        <button className="btn-primary w-full" disabled={submitting} type="submit">
+          {submitting ? "登录中..." : "登录"}
+        </button>
+      </form>
+    </div>
+  );
+}