[codex] Fix schedule edit completion payload

[jjoonleo]

Summary

• Remove latenessTime from schedule update requests so ordinary edits do not send completion data.
• Restore schedule update remote data source tests and add a regression check that edit payloads omit completion fields.

Root Cause

The edit flow built an update payload with latenessTime: 0. Elsewhere in the app, finishing a schedule with lateness time 0 maps to a normal completion, so the backend could treat an edited schedule as finished. Finished schedules are delete-only in the detail UI and are filtered out of upcoming schedules.

Validation

• flutter test test/data/data_sources/schedule_remote_data_source_test.dart test/data/repositories/schedule_repository_impl_stream_test.dart test/domain/use-cases/get_nearest_upcoming_schedule_use_case_test.dart
• flutter analyze

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