fix: respect terminal font override settings

[HarunOr]

Closes #285

Summary

• Apply terminalFontFamily when constructing xterm terminals.
• Apply terminalFontSize instead of hardcoding 13.
• Keep terminal zoom render-scaling based on the configured base font size.
• Add regression coverage for default and configured terminal font settings.

[Anton-Horn]

Thanks for the PR. Well scoped, seems like the settings slipped through after some refactoring. Will merge once CI ran through.