feat(portal): improve token handling and add 404 page

- Preserve URL path when processing tokens instead of always redirecting to root
- Add NotFound component for better UX on invalid routes
- Enable proper deep linking to portal routes like /new and /destinations/{id}

This allows external applications to redirect users to specific portal pages
while maintaining authentication flow.

Author: leggetter

internal/portal/src/app.tsx

@@ -1,5 +1,5 @@
 import { useEffect, useState, createContext } from "react";
-import { BrowserRouter, Routes, Route } from "react-router-dom";
+import { BrowserRouter, Routes, Route, Link } from "react-router-dom";
 import DestinationList from "./scenes/DestinationsList/DestinationList";
 import { SWRConfig } from "swr";
 
@@ -18,6 +18,35 @@ type ApiClient = {
 
 export const ApiContext = createContext<ApiClient>({} as ApiClient);
 
+function NotFound() {
+  return (
+    <div style={{ 
+      textAlign: 'center', 
+      padding: '2rem',
+      maxWidth: '500px',
+      margin: '0 auto'
+    }}>
+      <h1 style={{ fontSize: '2rem', marginBottom: '1rem', color: '#374151' }}>
+        Page Not Found
+      </h1>
+      <p style={{ fontSize: '1rem', marginBottom: '2rem', color: '#6b7280' }}>
+        The page you're looking for doesn't exist.
+      </p>
+      <Link 
+        to="/" 
+        style={{ 
+          color: '#3b82f6', 
+          textDecoration: 'none',
+          fontSize: '1rem',
+          fontWeight: '500'
+        }}
+      >
+        ← Back to Destinations
+      </Link>
+    </div>
+  );
+}
+
 export function App() {
   const token = useToken();
   const tenant = useTenant(token ?? undefined);
@@ -72,6 +101,7 @@ export function App() {
                       path="/destinations/:destination_id/*"
                       Component={Destination}
                     />
+                    <Route path="*" Component={NotFound} />
                   </Routes>
                 </SWRConfig>
               </ApiContext.Provider>
@@ -108,7 +138,10 @@ function useToken() {
     if (token) {
       setToken(token);
       sessionStorage.setItem("token", token);
-      window.location.replace("/");
+      
+      // Preserve the current path from the browser
+      const currentPath = window.location.pathname;
+      window.location.replace(currentPath);
     }
   }, []);