Add loading spinners

[Alen983]

Improve user experience by showing loading spinners when content is being fetched.

Features:

1. Add spinners for video loading
2. Show loading state when fetching movie/series data
3. Display spinner during page transitions
4. Add skeleton screens for content lists

[Vandna0609]

Hi! I’d like to work on this issue.
Could you please assign it to me?