feat: migrate icons to SF Symbols, refactor explore tab, add collections/programs data layer

- Replace all Ionicons with native SF Symbols via expo-symbols SymbolView
- Create reusable Icon wrapper component (src/shared/components/Icon.tsx)
- Remove @expo/vector-icons and lucide-react dependencies
- Refactor explore tab with filters, search, and category browsing
- Add collections and programs data with Supabase integration
- Add explore filter store and filter sheet
- Update i18n strings (en, de, es, fr) for new explore features
- Update test mocks and remove stale snapshots
- Add user fitness level to user store and types

vitest.config.ts

@@ -35,7 +35,6 @@ export default defineConfig({
         'src/shared/services/sync.ts': { lines: 80 },
         'src/shared/services/analytics.ts': { lines: 80 },
         'src/shared/data/achievements.ts': { lines: 100 },
-        'src/shared/data/collections.ts': { lines: 100 },
         'src/shared/data/programs.ts': { lines: 90 },
         'src/shared/data/trainers.ts': { lines: 100 },
         'src/shared/data/workouts.ts': { lines: 100 },