feat(backend): add fallback index serving routing when website is missing

backend/src/index.ts

@@ -1,4 +1,5 @@
 import 'dotenv/config';
+import fs from 'fs';
 import path from 'path';
 import { fileURLToPath } from 'url';
 import cors from 'cors';
@@ -71,9 +72,34 @@ app.get('/{*path}', (req, res, next) => {
     return;
   }
   
-  res.sendFile(path.join(publicDir, 'index.html'), (err) => {
-    if (err) next();
-  });
+  // Serve the primary website if it exists
+  const websiteIndex = path.join(publicDir, 'index.html');
+  if (fs.existsSync(websiteIndex)) {
+    res.sendFile(websiteIndex, (err) => {
+      if (err) next();
+    });
+    return;
+  }
+  
+  // Fallback to games if present
+  const gamesIndex = path.join(publicDir, 'games/index.html');
+  if (fs.existsSync(gamesIndex)) {
+    res.sendFile(gamesIndex, (err) => {
+      if (err) next();
+    });
+    return;
+  }
+  
+  // Fallback to mobile if present
+  const mobileIndex = path.join(publicDir, 'mobile/index.html');
+  if (fs.existsSync(mobileIndex)) {
+    res.sendFile(mobileIndex, (err) => {
+      if (err) next();
+    });
+    return;
+  }
+  
+  next();
 });
 
 app.use((_req, res) => {