Add comprehensive E2E tests for pagination component demos

[klagrida]

Summary

This PR adds a complete suite of end-to-end tests for the pagination component using Playwright, covering 9 different pagination demo scenarios with 100+ test cases total.

Key Changes

• basic-pagination-demo.spec.ts: Tests core pagination functionality including navigation, page links, Previous/Next buttons, active state styling, and keyboard accessibility (15 tests)
• buttons-pagination-demo.spec.ts: Validates button-based pagination implementation with proper element types and attributes (8 tests)
• disabled-link-pagination-demo.spec.ts: Tests anchor-based pagination with disabled state handling using aria-disabled (9 tests)
• ellipsis-pagination-demo.spec.ts: Verifies ellipsis rendering and behavior for large page counts with proper accessibility attributes (7 tests)
• first-page-pagination-demo.spec.ts: Tests pagination starting on page 1 with proper button states and navigation (8 tests)
• keyboard-navigation-pagination-demo.spec.ts: Comprehensive keyboard navigation tests including First/Last buttons, page size selector, and aria-labels (13 tests)
• last-page-pagination-demo.spec.ts: Tests pagination starting on the last page with proper state management (9 tests)
• many-pages-pagination-demo.spec.ts: Tests pagination with 20 pages, ellipsis behavior, and navigation across large page ranges (9 tests)
• page-size-pagination-demo.spec.ts: Tests dynamic page size selection and its impact on pagination state (10 tests)

Notable Implementation Details

• All tests follow consistent patterns using Playwright's locator API with custom attributes (sc-pagination, sc-pagination-link, etc.)
• Comprehensive accessibility testing including aria-current, aria-disabled, aria-label, and aria-hidden attributes
• Tests validate both visual state (CSS classes) and semantic HTML structure
• Keyboard navigation thoroughly tested including Tab, Enter, and focus management
• Tests cover edge cases like disabled states at boundaries, ellipsis rendering logic, and page size changes
• Each demo test file is self-contained with proper setup via beforeEach hooks

https://claude.ai/code/session_01B6kSDVZhWZGycgX3H4QMfg