Rewrite pay-rule-set E2E tests for full pipeline coverage

Tests now exercise the complete flow: create PayRuleSet, assign it to a
worker via the Plannings AssignedSite dialog, register working hours for
specific days, save, export Excel, and verify the export structure.
Replaced excessive waitForTimeout calls with proper element waits.
Reduced from 3 to 2 focused scenarios (Standard Agriculture + Apprentice).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: renemadsen