fix(beszel): add reliable live stats and filesystem UI (#6289)

apps/nextjs/src/env.ts

@@ -4,6 +4,7 @@ export const env = createEnv({
   server: {
     UNSAFE_ENABLE_MOCK_INTEGRATION: createBooleanSchema(false),
     DEMO_MODE: createBooleanSchema(false),
+    DEMO_READ_ONLY: createBooleanSchema(true),
   },
   experimental__runtimeEnv: process.env,
 });