feat: implement alias strategy for receipt import with user-scoped and global fallback, enhance validation and normalization, and update UI components

flutter/lib/features/import/data/import_repository.dart

@@ -265,7 +265,6 @@ class ImportRepository {
   /// - Learning unit mappings
   Future<Map<String, dynamic>> saveReceipt({
     required List<Map<String, dynamic>> items,
-    bool isAdminLearning = false,
     String? token,
   }) async {
     try {
@@ -280,7 +279,6 @@ class ImportRepository {
         },
         body: jsonEncode({
           'items': items,
-          if (isAdminLearning) 'isAdminLearning': true,
         }),
       ).timeout(
         const Duration(seconds: 60),

flutter/lib/features/import/data/receipt_import_session.dart

@@ -16,6 +16,8 @@ enum CategorySelectionSource { ai, manual }
 class ItemEdit {
   final int? productId;
   final String? productName;
+  final bool learnAlias;
+  final bool learnAliasGlobally;
   final int? categoryId;
   final String? categoryPath;
   final CategorySelectionSource? categorySource;
@@ -29,6 +31,8 @@ class ItemEdit {
   const ItemEdit({
     this.productId,
     this.productName,
+    this.learnAlias = false,
+    this.learnAliasGlobally = false,
     this.categoryId,
     this.categoryPath,
     this.categorySource,
@@ -85,6 +89,8 @@ class ReceiptImportSession {
     'edits': edits.map((key, value) => MapEntry(key.toString(), {
       'productId': value.productId,
       'productName': value.productName,
+      'learnAlias': value.learnAlias,
+      'learnAliasGlobally': value.learnAliasGlobally,
       'categoryId': value.categoryId,
       'categoryPath': value.categoryPath,
       'categorySource': value.categorySource?.name,
@@ -114,6 +120,8 @@ class ReceiptImportSession {
       edits[idx] = ItemEdit(
         productId: (value['productId'] as num?)?.toInt(),
         productName: value['productName'] as String?,
+        learnAlias: value['learnAlias'] == true,
+        learnAliasGlobally: value['learnAliasGlobally'] == true,
         categoryId: (value['categoryId'] as num?)?.toInt(),
         categoryPath: value['categoryPath'] as String?,
         categorySource: switch (value['categorySource']) {