chore(mobile-app): 优化开屏资源和UI文案

- 删除36张帧动画图片减小包体积
- 静态开屏图片从3张改为2张
- 将"权益激活"改为"权益已激活"

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/mobile-app/lib/features/auth/presentation/pages/splash_page.dart

@@ -29,7 +29,7 @@ class _SplashPageState extends ConsumerState<SplashPage> {
   static const int _staticDisplaySeconds = 3;
 
   /// 静态图片数量
-  static const int _staticImageCount = 3;
+  static const int _staticImageCount = 2;
 
   /// 当前显示的静态图片索引 (1-based)
   late int _staticImageIndex;

frontend/mobile-app/lib/features/authorization/presentation/widgets/user_profile_dialog.dart

@@ -594,7 +594,7 @@ class _UserProfilePageState extends ConsumerState<UserProfilePage> {
               borderRadius: BorderRadius.circular(10),
             ),
             child: Text(
-              auth.benefitActive ? '权益激活' : '权益未激活',
+              auth.benefitActive ? '权益已激活' : '权益未激活',
               style: TextStyle(
                 fontSize: 11,
                 color: auth.benefitActive ? const Color(0xFF4CAF50) : const Color(0xFF9E9E9E),