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/login_user.go

@@ -45,6 +45,10 @@ func (h *LoginUserHandler) Handle(ctx context.Context, query LoginUserQuery) (*L
 		return nil, errors.ErrNotFound
 	}
 
+	if !user.EmailVerified {
+		return nil, errors.ErrEmailNotVerified
+	}
+
 	return &LoginUserResult{
 		UserID:   user.ID,
 		Email:    user.Email,