fix: 任务详情页 JWT 鉴权失败导致回退登录页

- TaskListPanel 用 React Router <Link> 替代原生 <a href>，避免整页刷新
- auth store 初始化时同步读取 token 设置 isAuthenticated，避免 useEffect 异步执行前 ProtectedRoute 误判未登录

frontend/src/components/TaskListPanel.tsx

@@ -1,5 +1,5 @@
 import { useEffect, useState, useCallback } from 'react'
-import { useParams } from 'react-router-dom'
+import { Link, useParams } from 'react-router-dom'
 import { getTasks } from '../api/project'
 import type { Task } from '../api/types'
 import StatusBadge from './StatusBadge'
@@ -67,9 +67,9 @@ export default function TaskListPanel() {
           </p>
         ) : (
           tasks.map(task => (
-            <a
+            <Link
               key={task.id}
-              href={task.status === 'completed' ? `/projects/${projectId}/tasks/${task.id}` : undefined}
+              to={task.status === 'completed' ? `/projects/${projectId}/tasks/${task.id}` : '#'}
               style={{
                 display: 'block',
                 padding: '12px 16px',
@@ -77,8 +77,12 @@ export default function TaskListPanel() {
                 textDecoration: 'none',
                 color: 'inherit',
                 cursor: task.status === 'completed' ? 'pointer' : 'default',
+                pointerEvents: task.status === 'completed' ? 'auto' : 'none',
                 transition: 'background 0.15s',
               }}
+              onClick={e => {
+                if (task.status !== 'completed') e.preventDefault()
+              }}
               onMouseEnter={e => {
                 if (task.status === 'completed')
                   (e.currentTarget as HTMLElement).style.background = 'var(--accent-dim)'
@@ -115,7 +119,7 @@ export default function TaskListPanel() {
                 )}
               </div>
               <PipelineStages currentStage={task.stage ?? null} status={task.status} />
-            </a>
+            </Link>
           ))
         )}
       </div>

frontend/src/stores/auth.ts

@@ -22,7 +22,7 @@ interface AuthState {
 
 export const useAuthStore = create<AuthState>((set) => ({
   user: null,
-  isAuthenticated: false,
+  isAuthenticated: getToken() !== null,
   loading: false,
   error: null,