Redirect / to /dashboard.html

Visiting the bare root path returned Express's default "Cannot GET /"
since there was no route or index.html for it. dashboard.js already
bounces to /login.html when the session check fails, so this one
redirect covers both logged-in and logged-out visitors.

src/app.js

@@ -53,6 +53,12 @@ app.get('/k/:token', (req, res) => {
   res.sendFile(path.join(__dirname, '..', 'public', 'kiosk.html'));
 });
 
+// dashboard.js itself bounces to /login.html if the session check fails,
+// so this one redirect covers both logged-in and logged-out visitors.
+app.get('/', (req, res) => {
+  res.redirect('/dashboard.html');
+});
+
 app.use(express.static(path.join(__dirname, '..', 'public')));
 
 app.use('/api', (req, res) => {