fix(ci): perf job — point Lighthouse at /fr/ and /en/, drop spa fallback

The previous PR enabled `--localize` on the production build, so the
output structure became `dist/apps/portal-shell/browser/{en,fr}/`
with no top-level `index.html`. Two CI breakages followed:

- `nx run portal-shell:serve-static` (lhci's `startServerCommand`)
  was configured with `spa: true`. The `@nx/web:file-server` executor
  reads that as "copy `<staticFilePath>/index.html` to `404.html` for
  SPA fallback". The source file no longer exists, so the executor
  crashes with `ENOENT … copyfile … index.html` and never opens the
  port.
- Even if the server had started, `lighthouserc.js` was targeting
  `http://localhost:4200/` which produces an `http-server` directory
  listing under the new layout. Lighthouse would have run against
  that, not the SPA.

Fixes:

- Drop `spa: true` from the `serve-static` target. The executor no
  longer attempts the missing copy. Deep-link fallback in production
  is the reverse proxy's job (it routes `/{en,fr}/anything` to the
  matching `index.html`); `nx serve-static` is only used for the
  perf gate and for local prod-build inspection of the entry points.
  For deep-link testing in dev, `nx serve` is the right tool.
- Update `lighthouserc.js` `url` list to `['http://localhost:4200/fr/',
  'http://localhost:4200/en/']`, matching the directive in ADR-0019
  that both locales clear the same performance bar.

apps/portal-shell/project.json

@@ -112,8 +112,7 @@
       "options": {
         "buildTarget": "portal-shell:build",
         "port": 4200,
-        "staticFilePath": "dist/apps/portal-shell/browser",
-        "spa": true
+        "staticFilePath": "dist/apps/portal-shell/browser"
       }
     }
   }