refactor: 重构聊天数据层至core并简化首页UI

apps/lib/core/chat/chat_api.dart

@@ -0,0 +1,28 @@
+import 'dart:typed_data';
+
+abstract class ChatApi {
+  Future<Map<String, dynamic>> createRun(Map<String, dynamic> runInput);
+
+  Future<Stream<String>> streamRunEvents(
+    String threadId, {
+    String? lastEventId,
+  });
+
+  Future<Map<String, dynamic>> fetchHistory({
+    String? threadId,
+    DateTime? beforeDate,
+  });
+
+  Future<Map<String, dynamic>> uploadAttachment({
+    required String threadId,
+    required String filename,
+    required String mimeType,
+    required Uint8List bytes,
+  });
+
+  Future<Uint8List> fetchAttachmentPreview(String previewPath);
+
+  Future<String> transcribeAudio(String filePath);
+
+  Future<void> cancelRun({required String threadId, required String runId});
+}