fix: resolve linting issues and add dropdown tabindex

Fixed ESLint error in header component:
- Added tabindex="-1" to dropdown menu for keyboard accessibility
- Ensures dropdown is focusable for screen readers

Auto-fixed formatting issues:
- Ran ESLint --fix to auto-correct stylistic issues
- Fixed key spacing in achievement constants
- Fixed object key ordering

Test Results:
- ✅ All 123 tests passing (1 API + 122 shared-types)
- ✅ Frontend linting passes
- ✅ Only non-critical warnings remain in e2e and shared-types

apps/frontend/src/app/components/header/header.component.ts

@@ -58,6 +58,7 @@ import { ApiService } from '../../services/api.service';
                   class="dropdown-menu"
                   role="menu"
                   aria-label="User menu"
+                  tabindex="-1"
                   (keydown.escape)="closeDropdown()"
                 >
                   <a [routerLink]="['/profile', user.slug || user.id]" class="dropdown-item" role="menuitem" (click)="closeDropdown()">My Profile</a>