Fix side margins on tablet screens in zimui

[dan-niles]

Changes:

• Fix side margins on tablet screens so that the content fills the entire screen.
• Modify playlist panel height calculation so that the panel fits screen vertically.

Before:

After:

Fix #252

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 1.62%. Comparing base (a34f5e8) to head (ba57d50).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #255 +/- ## ===================================== Coverage 1.62% 1.62% ===================================== Files 11 11 Lines 1047 1047 Branches 158 158 ===================================== Hits 17 17 Misses 1030 1030 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.