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

common/Index.ets

@@ -0,0 +1,5 @@
+export { TrulyMEMConstants } from './src/main/ets/constant/TrulyMEMConstants';
+export { GraphDatabase, RecallEntity, TimeRangeParams } from './src/main/ets/model/GraphDatabase';
+export { GraphMemoryService } from './src/main/ets/service/GraphMemoryService';
+export { AIAgentService, ChatMessage, AgentResponse } from './src/main/ets/service/AIAgentService';
+export { ImmersiveTabNavigation } from './src/main/ets/component/ImmersiveTabNavigation';