- Add `splashScreenEnabled` preference to UserPreferences with default true
- Implement `SplashScreen` composable with animated logo, scale/fade transitions, and gradient background
- Add splash screen toggle in settings UI under "Interface" section
- Update navigation graph to conditionally show splash before dashboard when enabled
- Replace app launcher icons with SafeBite logo drawable
- Add `saveCroppedImage` helper to center-crop photos to square, resize to 512px, and compress to JPEG
- Apply cropping to both camera capture and gallery picker in `ListDetailScreen` and `ItemDetailSheet`
- Display custom item photos in tiles with `AsyncImage` and camera badge overlay
- Show full-width photos in item detail sheet
- Redesign onboarding "How it works" step
- Add camera/gallery photo capture for custom shopping list items with name and description fields
- Implement `addCustomItemWithImage` in `ListDetailViewModel` to create items with attached photos
- Add "Add to list" button in `ResultScreen` with list picker bottom sheet for scanned products
- Extend `ResultViewModel` with `addToList` method to save scanned products to shopping lists
- Add `PhotoSource
