feat: add admin dashboard, audit logs, token expiry check and test suite

Frontend Features:
- Add ProtectedRoute component with token expiry validation
- Create AdminDashboardPage with system statistics and user management
- Create AuditLogsPage with filtering and pagination
- Add admin-only navigation (Shield icon) for ymirliu@panjit.com.tw
- Add admin API methods to apiV2 service
- Add admin type definitions (SystemStats, AuditLog, etc.)

Token Management:
- Auto-redirect to login on token expiry
- Check authentication on route change
- Show loading state during auth check
- Admin privilege verification

Backend Testing:
- Add pytest configuration (pytest.ini)
- Create test fixtures (conftest.py)
- Add unit tests for auth, tasks, and admin endpoints
- Add integration tests for complete workflows
- Test user isolation and admin access control

Documentation:
- Add TESTING.md with comprehensive testing guide
- Include test running instructions
- Document fixtures and best practices

Routes:
- /admin - Admin dashboard (admin only)
- /admin/audit-logs - Audit logs viewer (admin only)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/src/App.tsx

@@ -1,5 +1,4 @@
 import { Routes, Route, Navigate } from 'react-router-dom'
-import { useAuthStore } from '@/store/authStore'
 import LoginPage from '@/pages/LoginPage'
 import UploadPage from '@/pages/UploadPage'
 import ProcessingPage from '@/pages/ProcessingPage'
@@ -7,20 +6,10 @@ import ResultsPage from '@/pages/ResultsPage'
 import ExportPage from '@/pages/ExportPage'
 import SettingsPage from '@/pages/SettingsPage'
 import TaskHistoryPage from '@/pages/TaskHistoryPage'
+import AdminDashboardPage from '@/pages/AdminDashboardPage'
+import AuditLogsPage from '@/pages/AuditLogsPage'
 import Layout from '@/components/Layout'
-
-/**
- * Protected Route Component
- */
-function ProtectedRoute({ children }: { children: React.ReactNode }) {
-  const isAuthenticated = useAuthStore((state) => state.isAuthenticated)
-
-  if (!isAuthenticated) {
-    return <Navigate to="/login" replace />
-  }
-
-  return <>{children}</>
-}
+import ProtectedRoute from '@/components/ProtectedRoute'
 
 function App() {
   return (
@@ -44,6 +33,24 @@ function App() {
         <Route path="export" element={<ExportPage />} />
         <Route path="tasks" element={<TaskHistoryPage />} />
         <Route path="settings" element={<SettingsPage />} />
+
+        {/* Admin routes - require admin privileges */}
+        <Route
+          path="admin"
+          element={
+            <ProtectedRoute requireAdmin>
+              <AdminDashboardPage />
+            </ProtectedRoute>
+          }
+        />
+        <Route
+          path="admin/audit-logs"
+          element={
+            <ProtectedRoute requireAdmin>
+              <AuditLogsPage />
+            </ProtectedRoute>
+          }
+        />
       </Route>
 
       {/* Catch all */}