fix(portal-bff): use bracket notation for process.env access

The strict-TS option noPropertyAccessFromIndexSignature: true (set in
tsconfig.base.json per ADR-0004) forbids dot-notation access on index
signatures. process.env is typed as { [key: string]: string | undefined }
so process.env.PORT must be written process.env['PORT']. The Nx
generator wrote the dot form by default; fix to comply with the
project's strict-TS bar.

Touched: portal-bff main.ts and the three portal-bff-e2e support files
(global-setup, global-teardown, test-setup).

apps/portal-bff/src/main.ts

@@ -18,7 +18,7 @@ async function bootstrap() {
 
   const globalPrefix = 'api';
   app.setGlobalPrefix(globalPrefix);
-  const port = process.env.PORT || 3000;
+  const port = process.env['PORT'] || 3000;
   await app.listen(port);
   Logger.log(`Application is running on: http://localhost:${port}/${globalPrefix}`);
 }