fix: toggle timestamps now properly hides/shows timestamps when toggled (resolves #5142)

[ariane-emory]

Fixes #5142 where 'Toggle timestamps' command was not actually hiding timestamps. The issue was inverted logic - when showTimestamps was false, it still displayed a shorter timestamp instead of hiding it completely.

• Wrap timestamp display in conditional Show component
• Only render timestamp when showTimestamps() is true
• Preserve existing timestamp format when visible