docs: add Plan 02 - Data Layer & Permission Flow implementation plan
21 bite-sized tasks covering domain models, CalendarContract data layer
(Cursor mappers with §8 defensive validation, ContentObserver-backed
SharedFlow repository), DataStore-persisted hidden-calendar set, Hilt
wiring, READ_CALENDAR permission flow (rationale + denied recovery), and
a wegwerfbarer Debug screen that visually validates data is flowing.
Out of scope: Month/Week/Day views (Plans 03-05), Event Detail Sheet
(Plan 06), Filter/Settings (Plan 07).
Jean-Luc Makiola
ed680b4482