test: add e2e tests for dashboard hub

[OlhaTmlk]

Description

Adds comprehensive E2E test coverage for the Dashboard Hub feature. All tests follow a create/test/cleanup pattern to leave the environment in its original state.

New test suites added:

editing-dashboard.spec.ts (6 new tests):

• Dashboard Hub - Page Rendering: hub heading, create button, table with Homepage/Name/Last Modified columns
• Dashboard Hub - Create Blank Dashboard: create from blank → verify in table → cleanup delete
• Dashboard Hub - Duplicate Dashboard: duplicate via table action → verify notification + table entry → cleanup
• Dashboard Hub - Delete Dashboard: create → navigate → delete via kebab → verify removed from hub
• Dashboard Hub - Navigation: hub → dashboard → breadcrumb back to hub
• Generic Dashboard Page - Rendering: header controls (title, edit name, add widgets, kebab), breadcrumb, and kebab menu items (Set as homepage, Duplicate, Copy config string, Delete)

widget-layout.spec.ts (4 new tests, 1 replaced):

• Empty Dashboard: replaced mock-based test with real create/set-homepage/test/restore/cleanup flow that verifies auto-open drawer on empty dashboard
• Extracted symbolic timeout constants (PAGE_LOAD_TIMEOUT_MS, WIDGET_LOAD_TIMEOUT_MS, DRAWER_TIMEOUT_MS)

Total: 22 E2E tests (11 per file)

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Checklist ☑️

• PR only fixes one issue or story
• Change reviewed for extraneous code
• UI best practices adhered to
• All PR checks pass locally (build, lint, test, E2E)

[OlhaTmlk]

/retest

[red-hat-konflux]

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[OlhaTmlk]

/retest