- Create firka_common package with core helpers (debug, json, icon), theme,
and shared widgets (FirkaCard, FirkaShadow, GradeWidget, GradeSmallCard,
ClassIconWidget, FirkaIconWidget, DelayedSpinnerWidget, CounterDigitWidget)
- Keep Isar models (GenericCacheModel, TimetableCacheModel, HomeworkCacheModel,
DatedCacheEntry, util) in firka and firka_wear - not moved to firka_common
- Update firka and firka_wear to depend on firka_common for shared UI only
- Add configurable roundGrade thresholds for firka settings
- Add package param to FirkaIconWidget for app asset paths
