[Frontend] Implement skeleton loading states for all data-dependent views

[Penielka]

Overview

Add skeleton screen placeholders for all views that fetch data to improve perceived performance.

Acceptance Criteria

• Skeleton components matching layout shapes
• Applied to course listings, profile, credentials, dashboards
• Animation (shimmer effect)
• Graceful transition to loaded content
• Consistent with existing LoadingFallback component

Priority: Medium

Reduces perceived loading time and layout shift.

[Richardkingz2019]

i would love to work on this issue

[grantfox-oss]

🦊 GrantFox — @Richardkingz2019 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #268)
2. Your PR will be reviewed by the AetherEdu maintainers

Good luck! Track your progress on GrantFox.