[Feature Request]: Add Bookmarked Playlist to Sidebar

### 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

FreeTube has the ability to mark a playlist as the playlist where your bookmarks go, but there is no link to that playlist in the sidebar.

This is a request to add a link with an new icon to the sidebar.

Note: This is specifically for the starred/pinned playlist in the playlist section. Similar to what #9536 initially suggested, and full list of playlists as was discussed in #4594.

**The Current Sidebar**

### Proposed Solution

I'm still digging through the code, but the ideal solution seems to be to retrieve the bookmarked playlist from its settings and add a link to a route that redirects to it in the sidebar.

### Alternatives Considered

Adding a setting to the settings page that lists any common playlists that would be bookmarked might be an option, but seems more cumbersome than doing it dynamically.

### Issue Labels

ease of use improvement

### FreeTube Version

v0.25.3 Beta

### Operating System Version

Ubuntu 2026.04

### Installation Method

.deb

### Upload screenshots or videos

_No response_

### Additional Information

_No response_

Start by locating the sidebar, the starred or pinned playlist setting, and the routing used to open playlists. Confirm how the bookmarked playlist is stored and how sidebar links navigate to playlists. Done means the configured bookmarked playlist appears in the sidebar with a new icon and opens the correct playlist.

Written by the indexing model from the issue text.