feat(auth): 鉴权片2 —— 前端登录闭环 + 保护路由 + 去掉 header 兜底

把 JWT 鉴权从后端核心闭环到端到端：

后端：
- middleware.RequireAuth：上下文无已验证 uid 则 401；挂在 owner 作用域业务路由组。
- 路由拆 公开/受保护：公开=auth/health + 按 task_id 寻址的 SSE 与报告导出
  （EventSource/下载无法带 Bearer）；受保护=tasks/memory/kb*/agents/reports/billing。
- userID(c) 去掉 X-User-ID 兜底，仅信任 JWT 注入的 uid。
- 修 CORS：Allow-Headers 增 Authorization（否则浏览器拦截带 Bearer 的请求）。

前端：
- lib/api：token 存 localStorage + Bearer 头（不再发 X-User-ID）+ authRegister/Login/Me
  + 401 清令牌并广播 sdx:logout；submitTask/report/memory/列表加载走 Bearer 与 401 守卫。
- views/Login：登录/注册全屏门。
- App：启动校验令牌 → 无则渲染 Login，有则进主应用；identity.userId=已验证 user.id；
  监听 sdx:logout 回登录页。
- TopBar：去掉可编辑身份输入，改显登录用户 + 登出。

实跑验证（docker+gateway+preview）：
- RequireAuth：无 token /kb/list、/agents → 401；/health → 200；带 token → 200。
- 前端：无 token 显登录门；注入有效 token 重载 → 进主应用、顶栏显 Dexter、KB 加载本人库、
  隔离徽标显雪花 uid。控制台无错、生产构建通过。
- 过程中发现并修复 CORS 缺 Authorization 头的真实 bug。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

sundynix-desktop/frontend/src/views/Login.tsx

@@ -0,0 +1,72 @@
+import { useState } from "react";
+import { LogIn, UserPlus, Loader2 } from "lucide-react";
+import { authLogin, authRegister, type AuthUser } from "../lib/api";
+import { Button, Input, Field } from "../ui";
+
+// Login：未登录时的全屏鉴权门。登录/注册成功后回调 onAuthed 把用户交给 App。
+export function Login({ onAuthed }: { onAuthed: (u: AuthUser) => void }) {
+  const [mode, setMode] = useState<"login" | "register">("login");
+  const [email, setEmail] = useState("");
+  const [password, setPassword] = useState("");
+  const [name, setName] = useState("");
+  const [busy, setBusy] = useState(false);
+  const [err, setErr] = useState("");
+
+  const submit = async () => {
+    if (busy) return;
+    setErr("");
+    setBusy(true);
+    try {
+      const u = mode === "login" ? await authLogin(email.trim(), password) : await authRegister(email.trim(), password, name.trim());
+      onAuthed(u);
+    } catch (e) {
+      setErr((e as Error).message);
+    } finally {
+      setBusy(false);
+    }
+  };
+
+  const isRegister = mode === "register";
+  return (
+    <div className="flex h-screen w-screen items-center justify-center bg-ink-950 text-slate-200">
+      <div
+        className="pointer-events-none absolute inset-x-0 top-0 h-80 opacity-60"
+        style={{ background: "radial-gradient(60% 100% at 50% 0%, rgba(124,92,246,0.12), transparent 70%)" }}
+      />
+      <div className="relative w-[360px] rounded-xl border border-line bg-ink-900 p-6 shadow-card">
+        <div className="mb-1 flex items-center gap-2">
+          <div className="flex h-8 w-8 items-center justify-center rounded-lg bg-brand/20 text-brand-400 font-bold">S</div>
+          <span className="text-lg font-semibold text-slate-100">sundynix-agentix</span>
+        </div>
+        <p className="mb-5 text-xs text-slate-500">{isRegister ? "创建账户以开始" : "登录以继续"}</p>
+
+        <div className="space-y-3">
+          {isRegister && (
+            <Field label="昵称">
+              <Input value={name} onChange={(e) => setName(e.target.value)} placeholder="如 Dexter" autoFocus={isRegister} />
+            </Field>
+          )}
+          <Field label="邮箱">
+            <Input type="email" value={email} onChange={(e) => setEmail(e.target.value)} placeholder="you@example.com" autoFocus={!isRegister} onKeyDown={(e) => e.key === "Enter" && submit()} />
+          </Field>
+          <Field label="密码">
+            <Input type="password" value={password} onChange={(e) => setPassword(e.target.value)} placeholder={isRegister ? "至少 6 位" : "••••••••"} onKeyDown={(e) => e.key === "Enter" && submit()} />
+          </Field>
+        </div>
+
+        {err && <div className="mt-3 rounded-md bg-danger/10 px-3 py-2 text-xs text-danger">{err}</div>}
+
+        <Button variant="primary" className="mt-4 w-full justify-center" icon={busy ? Loader2 : isRegister ? UserPlus : LogIn} disabled={busy || !email.trim() || !password} onClick={submit}>
+          {busy ? "处理中…" : isRegister ? "注册并进入" : "登录"}
+        </Button>
+
+        <div className="mt-3 text-center text-[11px] text-slate-500">
+          {isRegister ? "已有账户？" : "还没有账户？"}
+          <button className="ml-1 text-brand-400 hover:underline" onClick={() => { setErr(""); setMode(isRegister ? "login" : "register"); }}>
+            {isRegister ? "去登录" : "去注册"}
+          </button>
+        </div>
+      </div>
+    </div>
+  );
+}