refactor(data): move dto and schemas out of services directory

src/data/schemas/chat/chat_sync_data.ts

@@ -0,0 +1,13 @@
+/**
+ * 消息同步响应
+ * 原始 Dart: ChatSyncData (lib/data/models/chat/chat_sync.dart)
+ */
+import { z } from "zod";
+
+export const ChatSyncDataSchema = z.object({
+  syncedCount: z.number(),
+  totalHistory: z.number(),
+});
+
+export type ChatSyncDataInput = z.input<typeof ChatSyncDataSchema>;
+export type ChatSyncDataData = z.output<typeof ChatSyncDataSchema>;