[Feature Request]: Playlist Drag and Drop Sorting Improvements

### Guidelines

- [x] I have [searched the issue tracker for open and closed issues](https://github.com/FreeTubeApp/FreeTube/issues?q=is%3Aissue+sort%3Arelevance-desc) that are similar to the feature request I want to file, without success.
- [x] I have searched the [documentation](https://docs.freetubeapp.io/) for information that matches the description of the feature request I want to file, without success.
- [x] This issue contains only one feature request.
- [x] I have read and agree to follow the [rules](https://docs.freetubeapp.io/community/rules/).

### Problem Description

Glad to see the drag and drop playlist sorting feature from #8681 now available! Thank you for continuing to improve this software~

Having used the feature for a little bit now, I'm noticing a few spots that could be improved for better UX.

The main issue I'm finding is that dragging up or down is done at the same pace, not speeding up the further one moves one's mouse. This can make it take quite a while to move a video in long playlists, which can be both annoying and less accessible for those with issues holding down a mouse button uninterrupted for so long. I've also noticed that the page doesn't start scrolling up until the video is dragged quite far up over the playlist header – the viewport that gets taken into account seems to be the whole window, rather than just the part with the playlist grid (in grid mode).

The other improvement I'd appreciate seeing with this new feature is tweaking the spacing between video rows. The addition of the area that can be used for dragging has created too much blank space between video rows in grid mode. Since that area only has the one central draggability indicator and is otherwise blank, it looks as though the blank space between video rows has been doubled.

### Proposed Solution

The speed of scrolling when dragging videos should ideally be relative to how far up/down the mouse is, like in many other similar implementations, so that the time needed to drag it to the top/bottom of a playlist is not proportional to the length of the playlist. It would also be good for the point at which scrolling gets triggered to take into account the playlist grid area in grid mode, rather than the whole window viewport (which includes the playlist header).

The blank space between video rows in grid mode should be removed/collapsed if the draggable space is there, so that the grid has a similar density as before.

### Alternatives Considered

None that come to mind, since I would consider these to be UX and UI issues with the new feature, rather than deliberate choices.

### Issue Labels

ease of use improvement, visual improvement

### FreeTube Version

v0.25.0 Beta

### Operating System Version

Windows 10, version 22H2

### Installation Method

.exe

### Upload screenshots or videos

_No response_

### Additional Information

_No response_

Start by locating the playlist drag-and-drop implementation introduced for #8681, then inspect how grid scrolling and row spacing are handled. Done means drag scrolling accelerates with pointer distance, uses the playlist grid area in grid mode, and removes the extra blank space between video rows without breaking sorting.

Written by the indexing model from the issue text.