refactor: 按 sample_in_harmonyos 多层模块化架构重构工程结构

- 新增 common/ 公共模块：模型、服务、组件、常量
- 新增 features/ 功能模块：graph(星图)、chat(聊天)、settings(设置)、commonbusiness
- 新增 products/phone 产品入口层：EntryAbility + Index + MainPage
- Index.ets 简化为纯路由入口，TabNavigation 移至 MainPage 统一管理
- 更新 build-profile.json5 注册所有新模块
- 迁移原始 entry/ 代码到分层架构，保持功能完整

features/chat/oh-package.json5

@@ -0,0 +1,11 @@
+{
+  "name": "@ohos/chat",
+  "version": "1.0.0",
+  "description": "TrulyMEM chat feature module",
+  "main": "Index.ets",
+  "author": "",
+  "license": "",
+  "dependencies": {
+    "@ohos/common": "file:../../common"
+  }
+}