Use camelCase sendReminderAt to match existing invoice columns; the
snake_case name caused dashboard queries to fail after deploy.
Co-authored-by: Cursor <cursoragent@cursor.com>
Restrict line item edits to draft invoices, auto-create drafts on clock-out,
and add sendReminderAt scheduling with dashboard due reminders.
Co-authored-by: Cursor <cursoragent@cursor.com>