[Prajwal-4121998]

…+ type-safe navigation

feat: type-safe Navigation 3

• Replaced string-based Screen sealed class with @serializable route classes
• CatalogRoute (object) and DetailRoute(productId: Int) as type-safe routes
• NavHost updated to composable and composable
• toRoute() for extracting navigation arguments
• Compile-time route safety: wrong argument types fail at build, not runtime

feat: feature:detail module

• DetailContract: DetailUiState data class, DetailIntent + DetailEffect sealed classes
• DetailViewModel: MVI single processIntent() entry point, ProductRepository injection (direct repo injection — no use case needed for single pass-through call)
• DetailScreen: transparent overlay top bar (back + share + cart), hero image with gradient overlay, content card overlapping hero (-48dp offset), brand label in primary + uppercase, rating pill, in-stock emerald badge, price with strikethrough + discount %, features bento grid, expandable description, static reviews section with avatar initials, sticky bottom bar
• DetailBottomBar: outlined wishlist button (border-2 primary), secondary-container Add to Cart button with shopping bag icon (Stitch spec)
• 6 ViewModel unit tests: initial state, load success, load not found, toggle wishlist, toggle description, navigate back effect, add to cart effect

ci: JaCoCo updated for feature:detail

• jacoco plugin applied, exec file at build/jacoco/testDebugUnitTest.exec
• DetailViewModel threshold added to coverage verification

deps: kotlinx-serialization added for type-safe navigation