Recurrence previously only supported 5 fixed rules with no interval.
Adds TaskItem.recurrenceInterval (optional, nil = 1, so every existing
task is unaffected), a stepper in the shared create/edit sheet, quick-add
NLP for phrases like "every 2 weeks"/"biweekly"/"fortnightly", and
threads the interval through both countdown widgets so their progress
bars size correctly for biweekly/etc tasks too.
Built on KC-69's consolidated RecurrenceRule engine. Verified two things
by actually compiling and running standalone swiftc drivers rather than
just reading: the core interval math (44/44, unchanged from KC-69) and
the new quick-add regex patterns against realistic phrases including
"look into tru housing options every two weeks" (11/11 passing).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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