Align scheduled-call E2E with the shared date/time picker - #75

What Changed

This PR aligns the scheduled video-call E2E flow with the shared date/time picker used by the current dev client.

• Waits for dateTimePickerModal and verifies that its contextual title is Schedule Call.
• Uses the shared date, hour, minute, AM/PM, and confirmation controls.
• Matches the current minute-precision success toast and reuses the same expected time for downstream message and call-list assertions.

Fixed Flow

1. Set up the users and open the call scheduling choices.
2. Choose Schedule.
3. Wait for the shared date/time picker, verify its call-specific title, fill the shared controls, and submit.
4. Verify the success toast, sender and recipient scheduled messages, and both users' call lists.

Why

The test still targeted the previous call-specific picker IDs even though the dev client now opens a shared date/time picker. The dialog was visibly open, but the obsolete locator reported it as missing. After correcting those selectors, the test also exposed an old seconds-precision toast expectation; the current client displays scheduled times to the minute.

Validation

• CI=true npx playwright test tests/videoCall.e2e.test.js --project=chromium --grep "schedule call: scheduled message appears and call listed for both users" --workers=1 --retries=0 --reporter=line
• node --check tests/videoCall.e2e.test.js
• git diff --check ca62609..HEAD

Stacked on #73.

Closes #74