ActivityIndicator upgrade

[azizbecha]

Is your feature request related to a problem? Please describe.
`ActivityIndicator is limited in customization and naming compared to modern UI needs.

Describe the solution you'd like

• Rename ActivityIndicator to Spinner
• Add more spinner variants

Describe alternatives you've considered
Using custom loaders or third-party spinner libraries.

Additional context
A Spinner component with multiple variants would improve flexibility and align better with Paper theme.