feat: add unit mapping functionality and confirmation dialog for unit changes in import process

flutter/lib/features/import/presentation/edit_dialog.dart

@@ -206,6 +206,11 @@ class _EditDialogState extends State<EditDialog> {
   }
 
   Future<void> _confirm() async {
+    final originalUnit = widget.current.unit ?? widget.item.unit;
+    final newUnit = _unitCtrl.text.trim().isEmpty ? originalUnit : _unitCtrl.text.trim();
+
+    await _confirmUnitChange(originalUnit!, newUnit);
+
     if (_entryMode == ImportProductEntryMode.create) {
       final trimmedName = _newProductNameCtrl.text.trim();
       if (trimmedName.isEmpty) {
@@ -281,6 +286,38 @@ class _EditDialogState extends State<EditDialog> {
     );
   }
 
+  Future<void> _confirmUnitChange(String originalUnit, String newUnit) async {
+    if (originalUnit == newUnit) return;
+
+    return showDialog<void>(
+      context: context,
+      barrierDismissible: false,
+      builder: (BuildContext context) {
+        return AlertDialog(
+          title: const Text('Bekräfta enhetsändring'),
+          content: Text(
+            'Du försöker ändra enheten från "$originalUnit" till "$newUnit". Vill du fortsätta med denna ändring?',
+          ),
+          actions: <Widget>[
+            TextButton(
+              child: const Text('Avbryt'),
+              onPressed: () {
+                _unitCtrl.text = originalUnit;
+                Navigator.of(context).pop();
+              },
+            ),
+            TextButton(
+              child: const Text('Bekräfta'),
+              onPressed: () {
+                Navigator.of(context).pop();
+              },
+            ),
+          ],
+        );
+      },
+    );
+  }
+
   // ── Build ──────────────────────────────────────────────────────────────────
 
   @override