refactor: move HarmonyOS project files from harmony/ to branch root

entry/src/main/ets/pages/MainPage.ets

@@ -0,0 +1,21 @@
+import { GraphDatabase } from '../model/GraphDatabase';
+import { GraphPage } from './GraphPage';
+import { ChatPage } from './ChatPage';
+
+@Component
+export struct MainPage {
+    @Prop db: GraphDatabase;
+
+    build() {
+        GridRow({ columns: { sm: 1, md: 2, lg: 2 }, gutter: { x: 8, y: 8 } }) {
+            GridCol({ span: { sm: 1, md: 1, lg: 1 } }) {
+                GraphPage({ db: this.db })
+            }
+            GridCol({ span: { sm: 1, md: 1, lg: 1 } }) {
+                ChatPage({ db: this.db })
+            }
+        }
+        .width('100%')
+        .height('100%')
+    }
+}