feat: persist calendar free windows with Week Ahead (Closes #1258)

tests/e2e/test_mobile_week_ahead_release.py

@@ -285,15 +285,20 @@ def test_release_artifact_plans_seven_touch_safe_mobile_dates(
                 page.locator("#week-capacity-file"),
                 page.locator("#week-capacity-start"),
                 page.locator("#week-capacity-end"),
+                page.locator("#keep-week-free-times"),
                 page.locator("#apply-week-capacities"),
             ):
                 bounds = control.bounding_box()
                 assert bounds and bounds["height"] >= 44
             assert page.evaluate("document.documentElement.scrollWidth <= window.innerWidth")
+            page.locator("#keep-week-free-times").check()
             page.locator("#apply-week-capacities").click()
             expect(capacity_import).to_be_hidden()
             expect(page.locator("#week-review")).to_be_visible()
             expect(first_day).to_contain_text("45 of 420 min")
+            assert saved[-1]["days"][0]["free_windows"] == [
+                {"start_time": "10:00", "end_time": "17:00"}
+            ]
 
             page.wait_for_function("() => !document.querySelector('#confirm-week-plan').disabled")
             confirm = page.locator("#confirm-week-plan")