Add optional email verification and registration control

Implemented email service infrastructure with SMTP support and optional email verification for self-hosted deployments. Registration flow now supports open/closed modes and hardcoded Apocapoc branding.

Key features:
- Email service with SMTP and template rendering
- Optional email verification (auto-verified without SMTP config)
- Registration modes: open/closed for access control
- Hardcoded Apocapoc branding (AppName, AppURL, DefaultFrom)
- Separate registration and login flows (registration no longer returns tokens)

internal/application/queries/refresh_token_test.go

@@ -59,6 +59,10 @@ func (m *mockUserRepositoryForRefresh) FindByEmail(ctx context.Context, email st
 	return nil, nil
 }
 
+func (m *mockUserRepositoryForRefresh) FindByVerificationToken(ctx context.Context, token string) (*entities.User, error) {
+	return nil, errors.ErrNotFound
+}
+
 func (m *mockUserRepositoryForRefresh) Update(ctx context.Context, user *entities.User) error {
 	return nil
 }