* feat: add configurable done flag to TODO states
* feat: stamp CLOSED for any configured done state
* feat: add DONE state option and done marker to settings
* chore: remove unused Item.CycleState
* chore: drop vestigial state constants, mention DONE add in settings help
* feat: add state form model and commit logic
* feat: wire state form update/view into settings dispatch
* feat: replace state add/edit with unified form, toggle done after creation
* consolidate AddState and AddDoneState
* add findState() helper
* feat: add datepicker dependency and init helper
* feat: calendar-first set-date modes with text fallback
* feat: initialize datepicker when opening set-date modes
* feat: render calendar and hints in set-date view
* chore: go mod tidy for bubble-datepicker direct dependency
Promotes github.com/ethanefung/bubble-datepicker from indirect to a
direct require (it is imported directly by internal/ui) and drops the
now-unused golang.org/x/text v0.3.8 checksums.
