[Issue #3523] styling fixes for auth header

[doug-s-nava]

Summary

Fixes #3523

Time to review: 10 mins

Changes proposed

Some follow up styling fixes after initial launch of client side auth

• css rule with magic number for lining up the mobile submenu removed
• active hover state for mobile button no longer has white background
• caret is white when active
• dropdown items are lighter green on hover

Context for reviewers

1. start on this branch with npm run dev
2. visit http://localhost:3000 and log in
3. VERIFY: at desktop width logged in header looks correct (see screenshots)
4. VERIFY: at mobile width logged in header looks correct (see screenshots)

Additional information

Desktop

Mobile

[andycochran]

To keep all the .mobile-nav-dropdown-uncollapsed-override stuff together, I think you could move this inside the rule.

.mobile-nav-dropdown-uncollapsed-override {
  ... // all the default rules
  @include at-media("desktop") {
    button:hover {
      background-color: white;
    }
  }
}