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

entry/src/main/ets/pages/Index.ets

@@ -0,0 +1,35 @@
+import { MainPage } from './MainPage';
+import { SettingsPage } from './SettingsPage';
+import { GraphDatabase } from '../model/GraphDatabase';
+
+@Entry
+@Component
+struct Index {
+    @State currentIndex: number = 0;
+    private db: GraphDatabase = new GraphDatabase();
+
+    aboutToAppear() {
+        this.db.init(getContext(this));
+    }
+
+    build() {
+        Column() {
+            Tabs({ index: this.currentIndex, barPosition: BarPosition.End }) {
+                TabContent() {
+                    MainPage({ db: this.db })
+                }
+                .tabBar('🌌 TrulyMEM')
+
+                TabContent() {
+                    SettingsPage()
+                }
+                .tabBar('⚙ 设置')
+            }
+            .width('100%')
+            .height('100%')
+            .onChange((index: number) => { this.currentIndex = index; })
+        }
+        .width('100%')
+        .height('100%')
+    }
+}