Align scheduled video-call E2E with the shared date/time picker #74

Problem

The scheduled video-call E2E test consistently fails after clicking Schedule:

• Test: Video Call Tests › schedule call: scheduled message appears and call listed for both users
• Failure: #callScheduleDateModal.active is not found
• Run: https://github.com/Liberdus/client-testing/actions/runs/31038516798/job/92416742101

The failure screenshot shows that the Schedule Call dialog is visibly open. The test is using the previous call-specific picker IDs, while the deployed dev client now opens the shared date/time picker.

After updating the picker selectors locally, the test also exposed an outdated toast-format assumption: the current client displays 4:00 PM, while the test expects 4:00:00 PM.

This was exposed after #68 allowed the video-call setup to complete and advance to the scheduling step.

Current test flow

Open the call menu
→ choose Schedule
→ wait for #callScheduleDateModal
→ fill #callScheduleDate, #callScheduleHour, #callScheduleMinute, and #callScheduleAmPm
→ click #confirmCallSchedule
→ expect a success-toast time containing seconds

Current client flow

Open the call menu
→ choose Schedule
→ wait for #dateTimePickerModal with title "Schedule Call"
→ fill the shared dateTimePicker controls
→ click #confirmDateTimePicker
→ display the scheduled time with minute precision

Acceptance criteria

• Wait for the shared date/time picker and verify its title is Schedule Call.
• Fill the shared date, hour, minute, and AM/PM controls.
• Submit through the shared picker control.
• Assert the success toast using the client's minute-precision time.
• Preserve the existing scheduled-message and both-users call-list assertions.
• The targeted scheduled-call test passes against the dev site in Chromium.