New screens:
- Category detail (workout/category/[id]): filtered workout list
with SwiftUI segmented Picker for level sub-filter
- Collection detail (collection/[id]): hero header with gradient,
stats (workouts/minutes/calories), numbered workout list
Root layout:
- Inter font loading (400-900 weights) via @expo-google-fonts
- SplashScreen integration for font loading gate
- Route config for all screens with appropriate animations
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
