Stabilize CI Playwright test job by making execution CI-aware

[Copilot]

The test GitHub Actions job was failing due to flaky navigation to external test targets during Playwright runs (net::ERR_ABORTED on login page loads). This PR makes Playwright execution CI-aware to reduce transient failures without changing local developer defaults.

• CI execution profile

  • Detects CI via process.env.CI.
  • Runs tests non-parallel in CI (workers: 1, fullyParallel: false) to avoid concurrent navigation pressure on external dependencies.

• Transient failure tolerance

  • Enables a single retry in CI (retries: 1) for intermittent network/navigation failures.
  • Preserves local behavior (workers: 3, fullyParallel: true, retries: 0).

• Scope

  • Single-file change in playwright.config.ts; no test logic or selectors modified.

const isCI = !!process.env.CI;

export default defineConfig({
  fullyParallel: !isCI,
  retries: isCI ? 1 : 0,
  workers: isCI ? 1 : 3,
});