Rename app from "Shoppy" to "Shoppinguin" across codebase and documentation. Handle migration of legacy storage keys.

App.js

@@ -85,7 +85,7 @@ export default function App() {
       setManualPrices(nextPrices || {});
       setRecentProducts(Array.isArray(nextRecent) ? nextRecent : []);
       setIsHydrated(true);
-    }).catch(() => setStorageError('Bitte starte Shoppy erneut, um die lokalen Daten zu laden.'));
+    }).catch(() => setStorageError('Bitte starte Shoppinguin erneut, um die lokalen Daten zu laden.'));
   }
 
   useEffect(() => {
@@ -378,7 +378,7 @@ export default function App() {
     if (!isHydrated) {
       return (
         <View style={styles.loading}>
-          <Text style={styles.loadingText}>{storageError || 'Shoppy wird geladen...'}</Text>
+          <Text style={styles.loadingText}>{storageError || 'Shoppinguin wird geladen...'}</Text>
           {storageError ? <Text onPress={retryHydration} style={styles.retryText}>Erneut versuchen</Text> : null}
         </View>
       );