fix(qr): resolve scanner race condition and crashes

This commit addresses several issues related to the QR code scanner:

- Fixes a build failure by defining stable handlers (`handleRestoreClose`, `handleRestoreError`) for the QRScanner component in `App.tsx` using `useCallback`.
- Resolves a race condition that caused an `AbortError` when the scanner was initialized, particularly in React Strict Mode. This was fixed by ensuring all props passed to the scanner are stable.
- Implements more robust error handling within the `QRScanner` component to prevent crashes when `null` or `undefined` errors are caught.
- Updates documentation (`README.md`, `GEMINI.md`) to version 1.4.5.

src/components/QRScanner.tsx

@@ -70,22 +70,14 @@ export default function QRScanner({ onScanSuccess, onClose, onError }: QRScanner
                             // jsQR gives us raw bytes!
                             const rawBytes = code.binaryData;
 
-                            console.log('🔍 Raw QR bytes:', rawBytes);
-                            console.log('  - Length:', rawBytes.length);
-                            console.log('  - Hex:', Array.from(rawBytes).map((b: number) => b.toString(16).padStart(2, '0')).join(''));
-
                             // Detect binary (16 or 32 bytes with non-printable chars)
                             const isBinary = (rawBytes.length === 16 || rawBytes.length === 32) &&
                                 /[\x00-\x08\x0B\x0C\x0E-\x1F\x7F-\xFF]/.test(String.fromCharCode(...Array.from(rawBytes)));
 
-                            console.log('📊 Is binary?', isBinary);
-
                             if (isBinary) {
-                                console.log('✅ Passing Uint8Array');
                                 onScanSuccess(new Uint8Array(rawBytes));
                             } else {
                                 // Text QR - use the text property
-                                console.log('✅ Passing string:', code.data.slice(0, 50));
                                 onScanSuccess(code.data);
                             }
 
@@ -94,9 +86,33 @@ export default function QRScanner({ onScanSuccess, onClose, onError }: QRScanner
                     }, 300);
                 }
             } catch (err: any) {
+                // IMPORTANT: Check for null/undefined err object first.
+                if (!err) {
+                    console.error('Caught a null or undefined error inside QRScanner.');
+                    return; // Exit if error is falsy
+                }
+
+                if (isCancelled || err.name === 'AbortError') {
+                    console.log('Camera operation was cancelled or aborted, which is expected on unmount.');
+                    return; // Ignore abort errors, they are expected on cleanup
+                }
+
                 console.error('Camera error:', err);
                 setHasPermission(false);
-                const errorMsg = 'Camera access was denied.';
+                
+                let errorMsg = 'An unknown camera error occurred.';
+                if (err.name === 'NotAllowedError') {
+                    errorMsg = 'Camera access was denied. Please grant permission in your browser settings.';
+                } else if (err.name === 'NotFoundError') {
+                    errorMsg = 'No camera found on this device.';
+                } else if (err.name === 'NotReadableError') {
+                    errorMsg = 'Cannot access the camera. It may be in use by another application or browser tab.';
+                } else if (err.name === 'OverconstrainedError') {
+                    errorMsg = 'The camera does not meet the required constraints.';
+                } else if (err instanceof Error) {
+                    errorMsg = `Camera error: ${err.message}`;
+                }
+
                 setInternalError(errorMsg);
                 onError?.(errorMsg);
             }