fix(mobile-app): 移除pubspec.yaml中已删除的splash_frames目录

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

frontend/mobile-app/pubspec.yaml

@@ -108,7 +108,6 @@ flutter:
     - assets/images/backgrounds/
     - assets/images/avatars/
     - assets/images/illustrations/
-    - assets/images/splash_frames/
     - assets/images/splash_static/
     - assets/icons/
     - assets/icons/nav/