Fix: Add safe localStorage wrapper and QZ Tray toggle feature

- Created storage-utils.js with safeStorage wrapper to prevent tracking prevention errors
- Updated script.js to use safeStorage for theme persistence
- Added conditional QZ Tray connection based on 'Enable Scan to Boxes' toggle
- Fixed 404 error by removing non-existent /api/backup/path endpoint call
- Enhanced fg_scan.html to disable QZ Tray and socket connections when toggle is off
- Prevents console errors when browser tracking prevention blocks localStorage access

py_app/app/static/js/storage-utils.js

@@ -0,0 +1,40 @@
+/**
+ * Safe localStorage wrapper to handle tracking prevention errors
+ * This prevents console errors when browser tracking prevention blocks storage access
+ */
+const safeStorage = {
+    getItem: function(key) {
+        try {
+            return localStorage.getItem(key);
+        } catch (e) {
+            console.warn('localStorage access blocked:', e.message);
+            return null;
+        }
+    },
+    setItem: function(key, value) {
+        try {
+            localStorage.setItem(key, value);
+        } catch (e) {
+            console.warn('localStorage access blocked:', e.message);
+        }
+    },
+    removeItem: function(key) {
+        try {
+            localStorage.removeItem(key);
+        } catch (e) {
+            console.warn('localStorage access blocked:', e.message);
+        }
+    },
+    clear: function() {
+        try {
+            localStorage.clear();
+        } catch (e) {
+            console.warn('localStorage access blocked:', e.message);
+        }
+    }
+};
+
+// Export for use in other scripts
+if (typeof window !== 'undefined') {
+    window.safeStorage = safeStorage;
+}