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

app/privacy.tsx

@@ -7,7 +7,7 @@ import React from 'react'
 import { View, ScrollView, StyleSheet, Text, Pressable } from 'react-native'
 import { useSafeAreaInsets } from 'react-native-safe-area-context'
 import { useRouter } from 'expo-router'
-import Ionicons from '@expo/vector-icons/Ionicons'
+import { Icon } from '@/src/shared/components/Icon'
 
 import { useTranslation } from 'react-i18next'
 import { useHaptics } from '@/src/shared/hooks'
@@ -30,7 +30,7 @@ export default function PrivacyPolicyScreen() {
       {/* Header */}
       <View style={styles.header}>
         <Pressable style={styles.backButton} onPress={handleClose}>
-          <Ionicons name="chevron-back" size={28} color={darkColors.text.primary} />
+          <Icon name="chevron.left" size={28} color={darkColors.text.primary} />
         </Pressable>
         <Text style={styles.headerTitle}>{t('privacy.title')}</Text>
         <View style={{ width: 44 }} />