Feat/update session control

[unchihugo]

Summary

• Add session switcher functionality to taskbar widget context menu
• Update media flyout layout (slightly increase size of cover image, and width when media session is enabled)
• Update media flyout session switcher UI to use SplitButton; remove right click functionality

Type of Change

• Feature
• Bug fix
• Refactor (no functional changes)
• Style (formatting, naming)
• Other

Checklist

• Code changes are manually tested and working.
• Formatting and naming are consistent with the project.
• Self-review of changes is done.

• AI tools were used (if yes, I reviewed and fully understand the changes myself).