feat: 合并星图和聊天页面为 MainPage，响应式 GridRow 布局

- 新建 MainPage.ets，用 GridRow 响应式布局组合星图+聊天
- Index.ets 改为 2 Tab（TrulyMEM + 设置）
- GraphPage/ChatPage 接收 @Prop db 从父组件传入
- 恢复 README.md / README_EN.md 的特别鸣谢部分

harmonyos/trulymem-core/BuildProfile.ets

@@ -0,0 +1,17 @@
+/**
+ * Use these variables when you tailor your ArkTS code. They must be of the const type.
+ */
+export const HAR_VERSION = '1.0.0';
+export const BUILD_MODE_NAME = 'debug';
+export const DEBUG = true;
+export const TARGET_NAME = 'default';
+
+/**
+ * BuildProfile Class is used only for compatibility purposes.
+ */
+export default class BuildProfile { 
+	static readonly HAR_VERSION = HAR_VERSION;
+	static readonly BUILD_MODE_NAME = BUILD_MODE_NAME;
+	static readonly DEBUG = DEBUG;
+	static readonly TARGET_NAME = TARGET_NAME;
+}