Scrollbar in "Subscribe" Section Only Visible on Hover

https://github.com/user-attachments/assets/967321e9-f0ea-4304-905f-cf267c031fc5

#### **Description**
The scrollbar in the **"Subscribe"** section of the CHAOSS calendar page is only visible when hovered over. This makes it difficult for users to realize that more content is available and may lead to accessibility issues.

#### **Steps to Reproduce**
1. Open the CHAOSS calendar page.
2. Navigate to the "Subscribe" section on the left panel.
3. Observe that the scrollbar appears **only when hovered** over the section.

#### **Expected Behavior**
The scrollbar should be **always visible**, ensuring that users can easily scroll through the available subscription options.

#### **Additional Context**
- This change will improve **usability and accessibility** for users who may not immediately notice the scrollbar.
- The scrollbar width and colors can be adjusted to match the design language of the website.

#### **Type:** UI/UX Improvement

Start from the CHAOSS calendar page and inspect the left-panel "Subscribe" section where the scrollbar is only visible on hover. Update the relevant styling so the scrollbar remains visible, then verify the subscription options are clearly scrollable without hovering and that the appearance fits the website design.

Written by the indexing model from the issue text.