[BUG] Smooth-Scroll Animation Optimizations; Low Tab-Switching Framerate

### Please confirm these before moving forward

- [x] I have searched for my issue and have not found a work-in-progress/duplicate/resolved issue.
- [x] I have tested that this issue has not been fixed in the latest [(beta or stable) release](https://github.com/Devolutions/UniGetUI/releases/).
- [x] I have checked the [FAQ](https://github.com/Devolutions/UniGetUI#frequently-asked-questions) section for solutions.
- [x] This issue is about a bug (if it is not, please use the [correct template](https://github.com/Devolutions/UniGetUI/issues/new/choose)).

### UniGetUI Version

2026.2.5

### Windows version, edition, and architecture

25h2

### Describe your issue

https://github.com/user-attachments/assets/d251c5f6-511c-4f05-885b-e132403cb32a

Switching tab seems bit stuttery.

On another note, the current smooth-scrolling implementation seems quite computationally intensive. On my hardware the framerate drops visibly if the scrolling is fast.

Avalonia:

https://github.com/user-attachments/assets/4fe006d5-ddf5-4598-a846-2f25548863e5

WinUI:

https://github.com/user-attachments/assets/b3b3b607-cfc6-4526-b2ac-c77118512194

No source files, tests, or entry points are identified in the issue. Start by reproducing the tab-switching and fast smooth-scrolling behavior shown in the Avalonia and WinUI recordings, then locate the relevant UI paths and measure their frame rates; done means the stutter and scrolling frame drops are measurably improved without regressions.

Written by the indexing model from the issue text.