Add public profile pages and avatar hover cards

[icaroharry]

Summary

• add the public profile page flow, including the profile API route and profile UI components
• add avatar hover cards to home and mini-projetos discovery surfaces plus a Meu Perfil menu link
• fix the login/logout re-entry edge case and improve GitHub callback error reporting

Testing

• npx eslint app/components/_layouts/navbar/profile-menu.tsx app/components/_layouts/navbar/profile-menu.test.tsx app/components/ui/cards/challenge-card.tsx app/components/ui/cards/challenge-card.test.tsx app/components/ui/user-avatar-hover-card/index.tsx app/lib/models/user.server.ts app/lib/services/auth.server.ts app/lib/services/github-auth.server.ts app/routes/_api/user-profile/index.tsx app/routes/_landing-page/components/headline/avatars.tsx app/routes/_landing-page/components/headline/avatars.test.tsx app/routes/_layout-app/_auth/login/index.tsx app/routes/_layout-app/_auth/login/index.test.ts app/routes/_layout-app/_mini-projetos/mini-projetos/index.tsx app/routes/_layout-app/_mini-projetos/mini-projetos/featured-challenge-section.tsx app/routes/_layout-app/_perfil/components/profile-certificates.tsx app/routes/_layout-app/_perfil/components/profile-challenges.tsx app/routes/_layout-app/_perfil/components/profile-header.tsx app/routes/_layout-app/_perfil/components/profile-header.test.tsx app/routes/_layout-app/_perfil/components/profile-stats.tsx app/routes/_layout-app/_perfil/components/profile-stats.test.tsx 'app/routes/_layout-app/perfil/perfil.$github_user/index.tsx' 'app/routes/_layout-app/perfil/perfil.$github_user/index.test.tsx' app/routes/index.tsx
• npm run test:run -- 'app/components/_layouts/navbar/profile-menu.test.tsx' 'app/components/ui/cards/challenge-card.test.tsx' 'app/routes/_landing-page/components/headline/avatars.test.tsx' 'app/routes/_layout-app/_auth/login/index.test.ts' 'app/routes/_layout-app/perfil/perfil.$github_user/index.test.tsx'