Frontend E2E: dashboard creation flow

[roman1887]

We have Playwright E2E tests for the Predictive Intelligence wizard but none for dashboard creation. Add one that covers: create dashboard → add tile → save → reload page → tile is still there.

Where:

• File: create frontend/e2e/dashboard-creation.spec.ts
• Pattern: frontend/e2e/predictions.spec.ts (mocks the API instead of hitting a real backend)
• Fixtures helper: frontend/e2e/fixtures.ts

Acceptance:

• Test passes locally with npm run test:e2e
• Test passes in CI (the existing GitHub Action picks up new spec files automatically)

DEVEX (1)