Minimal testid additions to 4 renderer files so Playwright can target
stable selectors: table-renderer, cell-{rowId}-{fieldName}, kanban-board,
kanban-column-{label}, kanban-card-{rowId}, calendar-renderer,
inline-editor-input, inline-editor-readonly.
Also adds Dockerfile.e2e for the client build used in docker-compose.e2e.yml.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
