refactor: remove setup feature from build exports and config

Removes the `./setup` export entry from `package.json` and the
corresponding `src/features/setup/index.js` entry point from
`tsup.config.js`, eliminating the standalone setup feature module
from the public API and build output.

tsup.config.js

@@ -16,7 +16,6 @@ export default defineConfig([
       'src/core/api/index.js',
       'src/core/api/nx-route.js',
       'src/core/database/index.js',
-      'src/features/setup/index.js',
       'src/cli/database.js',
       'src/cli/setup.js',
       'src/core/email/index.js',