fix: update legacy runtime path

- Changed the legacy runtime path from 'legacy-runtime.js' to 'index.js'
in runtime configuration.
- Added a new start script (start.js) to check for the existence of the
built TypeScript server entrypoint and import it.

server/src/config/runtime.ts

@@ -14,7 +14,7 @@ export function getRuntimePaths(): RuntimePaths {
     serverSrcDir,
     serverDir,
     projectRoot: path.resolve(serverDir, '..'),
-    legacyRuntimePath: path.join(serverDir, 'legacy-runtime.js'),
+    legacyRuntimePath: path.join(serverDir, 'index.js'),
     bootstrapEntrypointPath: path.join(serverDir, 'dist', 'bootstrap.js'),
   };
 }