Implemented E2E test for setting milestone on an issue that has no milestone. ## Changes Made - Created new test file: tests/e2e/test_update_issue_set_milestone_from_none.py ## Test Cases (4 tests) 1. **test_update_issue_set_milestone_from_none** - Basic test: create issue without milestone, select milestone from dropdown, save, verify via API 2. **test_update_issue_set_milestone_from_none_using_search_filter** - Tests using search input to filter milestones before selection 3. **test_update_issue_set_milestone_from_none_with_multiple_milestones_available** - Tests selecting specific milestone when multiple options exist 4. **test_update_issue_set_milestone_from_different_project_milestones** - Tests milestone selection with milestones from multiple projects ## Verification - All 4 new tests pass - Existing 9 milestone E2E tests still pass (test_detail_modal_milestone.py) ## Pattern Follows the same structure as test_update_issue_set_project_from_none.py