Task Archiving: soft-delete completed tasks after N days

[TheSethRose]

Summary

Introduce soft archiving for completed tasks so older items are hidden without permanent deletion.

Current behavior

• Task removal is permanent via the delete flow in src/app/(dashboard)/tasks/TaskModal.tsx and src/app/api/tasks/route.ts.
• Status options in src/lib/task-statuses.ts do not include an archived state.
• docs/DATABASE.md has no archive metadata column.

Target behavior

• Add archive metadata (e.g., archived_at or a dedicated archived status).
• Exclude archived items from default task queries with a toggle to include them.
• Automatically archive completed tasks after a configurable retention window.
• Allow restore back to active status without data loss.

Scope

• DB migration for archive metadata.
• API changes to filter by archive state and restore on demand.
• UI filter and restore actions in tasks views.
• Worker/cron job to archive by retention policy.

Acceptance criteria

• Completed tasks enter archive state after the configured retention window.
• Archived tasks are hidden by default but visible via a filter.
• Restore action returns a task to its prior status and preserves notes.

Open questions

• Preferred default retention window (e.g., 14/30/60 days)?
• Archive as status vs. archived timestamp?

References

• docs/DATABASE.md
• src/lib/task-statuses.ts
• src/app/api/tasks/route.ts
• src/app/(dashboard)/tasks/TaskModal.tsx