[Redesign] Home nav normalization

Summary: Ref T8099, makes the home nav elements more resilient to font size changes, fixes alignment on mobile.

Test Plan: Review home nav with smaller and larger font, check hover states, check phone layouts.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D13465