[FEATURE] Option to turn key borders off

[keepieuppie10]

Problem / Use Case
Not a fan of borders

Proposed Solution
Option to remove borders

Privacy Consideration
Confirm this feature respects privacy-first principles (no network calls, no analytics, no data collection)
Yes

Additional Context (optional)
Better visuals

[cweiske]

This would also give a bit more space to make the key text larger, see #771.