feat: Optimize note encryption and decryption processes with parallel execution

lib/data/sync_models.dart

@@ -1,13 +1,12 @@
 import 'package:notas/models/note.dart';
 import 'package:notas/models/category.dart';
+import 'dart:convert';
 
 // DTOs para sincronización con el servidor
 
 class SyncRequest {
-  SyncRequest({
-    DateTime? lastSyncAt,
-    required this.changes,
-  }) : lastSyncAt = lastSyncAt ?? DateTime.utc(1970, 1, 1);
+  SyncRequest({DateTime? lastSyncAt, required this.changes})
+    : lastSyncAt = lastSyncAt ?? DateTime.utc(1970, 1, 1);
 
   final DateTime lastSyncAt;
   final SyncChanges changes;
@@ -21,10 +20,7 @@ class SyncRequest {
 }
 
 class SyncChanges {
-  const SyncChanges({
-    this.categories = const [],
-    this.notes = const [],
-  });
+  const SyncChanges({this.categories = const [], this.notes = const []});
 
   final List<SyncCategoryPayload> categories;
   final List<SyncNotePayload> notes;
@@ -33,8 +29,7 @@ class SyncChanges {
     return {
       if (categories.isNotEmpty)
         'categories': categories.map((c) => c.toJson()).toList(),
-      if (notes.isNotEmpty)
-        'notes': notes.map((n) => n.toJson()).toList(),
+      if (notes.isNotEmpty) 'notes': notes.map((n) => n.toJson()).toList(),
     };
   }
 }
@@ -49,7 +44,8 @@ class SyncChangesResponse {
   final List<SyncNoteResponse> notes;
 
   factory SyncChangesResponse.fromJson(Map<String, dynamic> json) {
-    final List<dynamic> categoriesJson = json['categories'] as List<dynamic>? ?? [];
+    final List<dynamic> categoriesJson =
+        json['categories'] as List<dynamic>? ?? [];
     final List<dynamic> notesJson = json['notes'] as List<dynamic>? ?? [];
 
     return SyncChangesResponse(
@@ -62,6 +58,30 @@ class SyncChangesResponse {
     );
   }
 }
+
+String _readStringValue(dynamic value) {
+  if (value is String) {
+    return value;
+  }
+  if (value == null) {
+    throw FormatException('Expected String value but found null');
+  }
+  return jsonEncode(value);
+}
+
+int _readIntValue(dynamic value) {
+  if (value is int) {
+    return value;
+  }
+  if (value is String) {
+    final int? parsed = int.tryParse(value);
+    if (parsed != null) {
+      return parsed;
+    }
+  }
+  throw FormatException('Expected int value but found $value');
+}
+
 class SyncCategoryPayload {
   const SyncCategoryPayload({
     required this.id,
@@ -163,11 +183,11 @@ class SyncResponse {
 
   factory SyncResponse.fromJson(Map<String, dynamic> json) {
     return SyncResponse(
-      serverTimestamp:
-          DateTime.parse(json['serverTimestamp'] as String),
+      serverTimestamp: DateTime.parse(json['serverTimestamp'] as String),
       synced: json['synced'] as bool? ?? false,
-        changes: SyncChangesResponse.fromJson(
-          json['changes'] as Map<String, dynamic>? ?? {}),
+      changes: SyncChangesResponse.fromJson(
+        json['changes'] as Map<String, dynamic>? ?? {},
+      ),
     );
   }
 }
@@ -189,9 +209,9 @@ class SyncCategoryResponse {
 
   factory SyncCategoryResponse.fromJson(Map<String, dynamic> json) {
     return SyncCategoryResponse(
-      id: json['id'] as String,
-      encryptedName: json['encrypted_name'] as String,
-      serverVersion: json['serverVersion'] as int,
+      id: _readStringValue(json['id']),
+      encryptedName: _readStringValue(json['encrypted_name']),
+      serverVersion: _readIntValue(json['serverVersion']),
       isDeleted: json['isDeleted'] as bool? ?? false,
       updatedAt: DateTime.parse(json['updatedAt'] as String),
     );
@@ -231,11 +251,13 @@ class SyncNoteResponse {
 
   factory SyncNoteResponse.fromJson(Map<String, dynamic> json) {
     return SyncNoteResponse(
-      id: json['id'] as String,
-      categoryId: json['categoryId'] as String?,
-      encryptedTitle: json['encrypted_title'] as String,
-      encryptedBody: json['encrypted_body'] as String,
-      serverVersion: json['serverVersion'] as int,
+      id: _readStringValue(json['id']),
+      categoryId: json['categoryId'] == null
+          ? null
+          : _readStringValue(json['categoryId']),
+      encryptedTitle: _readStringValue(json['encrypted_title']),
+      encryptedBody: _readStringValue(json['encrypted_body']),
+      serverVersion: _readIntValue(json['serverVersion']),
       position: json['position'] as int? ?? 0,
       isDeleted: json['isDeleted'] as bool? ?? false,
       updatedAt: DateTime.parse(json['updatedAt'] as String),