Handle error states and accessibility improvements

src/screens/ScanScreen.js

@@ -30,9 +30,15 @@ export default function ScanScreen({ preferences, productCache, onScanBarcode, o
 
     setIsScanning(false);
     setIsLoadingProduct(true);
-    const result = await onScanBarcode(event.data).finally(() => {
+    let result;
+
+    try {
+      result = await onScanBarcode(event.data);
+    } catch (error) {
+      result = { status: 'error', errorMessage: 'Das Produkt konnte gerade nicht geladen werden.' };
+    } finally {
       setIsLoadingProduct(false);
-    });
+    }
 
     if (result?.status !== 'found') {
       setScanError(result?.errorMessage || 'Der Barcode konnte nicht verarbeitet werden.');
@@ -41,10 +47,15 @@ export default function ScanScreen({ preferences, productCache, onScanBarcode, o
   }
 
   async function handleManualSearch() {
+    if (!manualSearchQuery.trim() || isSearching) return;
+
     setIsSearching(true);
-    const results = await searchProducts(manualSearchQuery, productCache, preferences.offlineModeEnabled);
-    setManualResults(results);
-    setIsSearching(false);
+    try {
+      const results = await searchProducts(manualSearchQuery, productCache, preferences.offlineModeEnabled);
+      setManualResults(results);
+    } finally {
+      setIsSearching(false);
+    }
   }
 
   function retryScan() {
@@ -98,6 +109,7 @@ export default function ScanScreen({ preferences, productCache, onScanBarcode, o
       <ManualSearchInput
         onChangeText={setManualSearchQuery}
         onSubmit={handleManualSearch}
+        disabled={isSearching}
         value={manualSearchQuery}
       />
       {isSearching ? <Text style={styles.note}>Suche läuft...</Text> : null}