fix: use Express 5 wildcard syntax for better-auth handler route

Express 5 (path-to-regexp v8+) dropped support for the *paramName
wildcard syntax from Express 4. The route registered as
'/api/auth/*authPath' silently fails to match any sub-path, causing
every /api/auth/* request to return 404 instead of reaching the
better-auth handler.

Fixes: #2898

Change the route to '/api/auth/{*authPath}', the correct named
catch-all syntax in Express 5.

server/src/app.ts

@@ -133,7 +133,7 @@ export async function createApp(
     });
   });
   if (opts.betterAuthHandler) {
-    app.all("/api/auth/*authPath", opts.betterAuthHandler);
+    app.all("/api/auth/{*authPath}", opts.betterAuthHandler);
   }
   app.use(llmRoutes(db));