feat(navigation): implement CRUD navigation and MainActivity integration
ui/navigation/Screen.kt:
- Sealed interface with @Serializable routes: ItemList, ItemForm,
CategoryManagement, LocationManagement
- ItemForm accepts optional itemId for edit mode (type-safe navigation)
ui/navigation/KrisenvorratNavGraph.kt:
- NavHost with ItemList as start destination
- Screen wiring: ItemList -> ItemForm (create/edit), CategoryManagement,
LocationManagement with back navigation via popBackStack()
ui/item/ItemListScreen.kt:
- Added onItemClick, onCategoriesClick, onLocationsClick callbacks
- TopAppBar MoreVert dropdown menu for category/location management
- ItemCard now clickable to navigate to edit mode
MainActivity.kt:
- Replaced placeholder with NavHost via KrisenvorratNavGraph
- rememberNavController() as root navigation controller
ui/navigation/ScreenTest.kt:
- 7 tests covering route instantiation, nullable itemId, equality
Closes #28
10d19f0321