fix: resolve im backend issue list regressions

server/db/mysql/tenant_entry.go

@@ -4,7 +4,10 @@
 package mysql
 
 import (
+	"database/sql"
 	"encoding/json"
+	"errors"
+	"strings"
 	"time"
 
 	"github.com/jmoiron/sqlx"
@@ -60,7 +63,17 @@ func (a *adapter) TenantApplicationCreate(application *t.TenantApplication) (*t.
 	if cancel != nil {
 		defer cancel()
 	}
-	_, err := db.ExecContext(ctx, `INSERT INTO im_tenant_applications
+	var existingID string
+	err := db.QueryRowContext(ctx, `SELECT application_id FROM im_tenant_applications
+		WHERE credit_code=? AND status IN ('received','pending','reviewing') ORDER BY id DESC LIMIT 1`,
+		strings.ToUpper(strings.TrimSpace(application.CreditCode))).Scan(&existingID)
+	if err == nil && existingID != "" {
+		return nil, t.ErrDuplicate
+	}
+	if err != nil && !errors.Is(err, sql.ErrNoRows) {
+		return nil, err
+	}
+	_, err = db.ExecContext(ctx, `INSERT INTO im_tenant_applications
 		(application_id,credit_code,enterprise_email,license_file_id,tenant_code_hint,client_context,idempotency_key,status,estimated_review_hour,submitted_at,created_at,updated_at)
 		VALUES(?,?,?,?,?,?,?,?,?,?,?,?)`,
 		application.ApplicationID, application.CreditCode, application.EnterpriseEmail, application.LicenseFileID,