feat: reorganize attachments provider and model structure

lib/dashbot/core/common/widgets/dashbot_action_buttons.dart

@@ -2,7 +2,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import '../../../features/chat/models/chat_models.dart';
 import '../../../features/chat/viewmodel/chat_viewmodel.dart';
-import '../../../features/chat/providers/attachments_provider.dart';
+import '../../providers/attachments_provider.dart';
 import 'package:file_selector/file_selector.dart';
 import '../../services/openapi_import_service.dart';
 import '../../../features/chat/view/widgets/openapi_operation_picker_dialog.dart';

lib/dashbot/core/model/chat_attachment.dart

@@ -0,0 +1,19 @@
+import 'package:flutter/services.dart';
+
+class ChatAttachment {
+  final String id;
+  final String name;
+  final String mimeType;
+  final int sizeBytes;
+  final Uint8List data;
+  final DateTime createdAt;
+
+  ChatAttachment({
+    required this.id,
+    required this.name,
+    required this.mimeType,
+    required this.sizeBytes,
+    required this.data,
+    required this.createdAt,
+  });
+}

lib/dashbot/core/providers/attachments_provider.dart

@@ -0,0 +1,40 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:apidash/utils/file_utils.dart';
+
+import '../model/chat_attachment.dart';
+
+class AttachmentsState {
+  final List<ChatAttachment> items;
+  const AttachmentsState({this.items = const []});
+
+  AttachmentsState copyWith({List<ChatAttachment>? items}) =>
+      AttachmentsState(items: items ?? this.items);
+}
+
+class AttachmentsNotifier extends StateNotifier<AttachmentsState> {
+  AttachmentsNotifier() : super(const AttachmentsState());
+
+  ChatAttachment add({
+    required String name,
+    required String mimeType,
+    required Uint8List data,
+  }) {
+    final att = ChatAttachment(
+      id: getNewUuid(),
+      name: name,
+      mimeType: mimeType,
+      sizeBytes: data.length,
+      data: data,
+      createdAt: DateTime.now(),
+    );
+    state = state.copyWith(items: [...state.items, att]);
+    debugPrint('[Attachments] Added ${att.name} (${att.sizeBytes} bytes)');
+    return att;
+  }
+}
+
+final attachmentsProvider =
+    StateNotifierProvider<AttachmentsNotifier, AttachmentsState>((ref) {
+  return AttachmentsNotifier();
+});