feat: fix OAuth email completion flow

backend/internal/handler/auth_linuxdo_oauth.go

@@ -383,6 +383,7 @@ func (h *AuthHandler) LinuxDoOAuthCallback(c *gin.Context) {
 		upstreamClaims,
 		compatEmail,
 		compatEmailUser,
+		emailVerificationRequired,
 		forceEmailOnSignup,
 	); err != nil {
 		redirectOAuthError(c, frontendCallback, "session_error", "failed to continue oauth login", "")
@@ -433,6 +434,7 @@ func (h *AuthHandler) createLinuxDoOAuthChoicePendingSession(
 	upstreamClaims map[string]any,
 	compatEmail string,
 	compatEmailUser *dbent.User,
+	emailVerificationRequired bool,
 	forceEmailOnSignup bool,
 ) error {
 	suggestionEmail := strings.TrimSpace(suggestedEmail)
@@ -467,6 +469,17 @@ func (h *AuthHandler) createLinuxDoOAuthChoicePendingSession(
 	if forceEmailOnSignup && compatEmailUser == nil {
 		completionResponse["choice_reason"] = "force_email_on_signup"
 	}
+	if (emailVerificationRequired || forceEmailOnSignup) && compatEmailUser == nil {
+		completionResponse["step"] = "create_account_required"
+		completionResponse["email_binding_required"] = true
+		completionResponse["force_email_on_signup"] = true
+		if emailVerificationRequired {
+			completionResponse["choice_reason"] = "email_verification_required"
+		}
+		delete(completionResponse, "email")
+		delete(completionResponse, "resolved_email")
+		resolvedChoiceEmail = ""
+	}
 
 	var targetUserID *int64
 	if compatEmailUser != nil && compatEmailUser.ID > 0 {