refactor(App, navigation): migrate to Expo Router and clean up navigation structure

- Updated App entry point to utilize Expo Router, simplifying the navigation setup.
- Removed legacy navigation components and services to streamline the codebase.
- Adjusted package.json to reflect the new entry point and updated dependencies for compatibility.
- Enhanced overall application structure by consolidating navigation logic and improving maintainability.

src/types/dto.ts

@@ -541,7 +541,8 @@ export type GroupRole = 'owner' | 'admin' | 'member';
 
 // 群组信息
 export interface GroupResponse {
-  id: number;
+  /** 应用内统一为十进制字符串（groupService 从 API 归一化），避免大整型精度问题 */
+  id: string;
   name: string;
   avatar: string;
   description: string;
@@ -556,7 +557,7 @@ export interface GroupResponse {
 // 群组成员信息
 export interface GroupMemberResponse {
   id: number;
-  group_id: number;
+  group_id: string;
   user_id: string;  // UUID字符串
   role: GroupRole;
   nickname: string;
@@ -568,7 +569,7 @@ export interface GroupMemberResponse {
 // 群公告信息
 export interface GroupAnnouncementResponse {
   id: number;
-  group_id: number;
+  group_id: string;
   content: string;
   author_id: string;  // UUID字符串
   is_pinned: boolean;