feat: add clear chat functionality

lib/dashbot/features/chat/view/pages/dashbot_chat_page.dart

@@ -1,3 +1,5 @@
+import 'package:apidash_design_system/apidash_design_system.dart';
+
 import '../../models/chat_models.dart';
 import '../widgets/chat_bubble.dart';
 import '../../viewmodel/chat_viewmodel.dart';
@@ -82,6 +84,17 @@ class _ChatScreenState extends ConsumerState<ChatScreen> {
             padding: const EdgeInsets.all(8.0),
             child: Row(
               children: [
+                ADIconButton(
+                  icon: Icons.clear_all_rounded,
+                  tooltip: 'Clear chat',
+                  onPressed: ref.watch(chatViewmodelProvider).isGenerating
+                      ? null
+                      : () {
+                          ref
+                              .read(chatViewmodelProvider.notifier)
+                              .clearCurrentChat();
+                        },
+                ),
                 Expanded(
                   child: TextField(
                     controller: _textController,

lib/dashbot/features/chat/viewmodel/chat_viewmodel.dart

@@ -284,6 +284,18 @@ class ChatViewmodel extends StateNotifier<ChatState> {
     state = state.copyWith(isGenerating: false);
   }
 
+ void clearCurrentChat() {
+    final id = _currentRequest?.id ?? 'global';
+    _sub?.cancel();
+    final newSessions = {...state.chatSessions};
+    newSessions[id] = [];
+    state = state.copyWith(
+      chatSessions: newSessions,
+      isGenerating: false,
+      currentStreamingResponse: '',
+    );
+  }
+
   Future<void> applyAutoFix(ChatAction action) async {
     final requestId = _currentRequest?.id;
     if (requestId == null) return;