fix: nested route navigation — use relative paths, redirect to / not /dashboard

frontend/src/App.tsx

@@ -43,7 +43,7 @@ function RedirectIfAuth({ children }: { children: ReactNode }) {
   const { isAuthenticated } = useAuth()
 
   if (isAuthenticated) {
-    return <Navigate to="/dashboard" replace />
+    return <Navigate to="/" replace />
   }
   return <>{children}</>
 }
@@ -143,7 +143,7 @@ function AppRoutes() {
             <AppLayout onSearch={handleSearch} onSearchNavigate={handleSearchNavigate}>
               <Suspense fallback={<Loading />}>
                 <Routes>
-                  <Route index element={<Navigate to="/dashboard" replace />} />
+                  <Route index element={<Navigate to="dashboard" replace />} />
                   <Route path="dashboard" element={<DashboardPage />} />
                   <Route path="gateway" element={<GatewayPage />} />
                   <Route path="health" element={<HealthPage />} />