Feature request: support task start times

[MaybeItsAdam]

Summary

Add support for task start times / start dates as first-class task parameters.

Motivation

Right now tasks have due-date-oriented workflows, but there is no way to represent:

• when work should begin
• when a task becomes active
• when something should appear in Today / This Week versus remain hidden until later

This would improve planning and make hide-future logic more useful.

Proposed behavior

Support a start field alongside due:

• start date
• optional start time
• due date remains separate

Examples:

• start tomorrow 09:00
• start next monday
• start 2026-04-10 14:00

Likely product impact

• command parsing
• filtering
• visibility logic
• board/planning workflows
• Google Calendar / scheduling integrations
• possible UI badges alongside due

Questions

• Should start time affect task visibility by default?
• Should hidden/future behavior use start date, due date, or both?
• How should overdue / due buckets behave for tasks with a future start?
• Does Checkvist support this natively, or do we need local metadata/plugin storage?

Possible follow-up

• "scheduled" bucket
• "available now" filtering
• auto-hide tasks until start time