fix(user,customer): return 409 on phone duplicate-key races

Map E11000 from the per-collection phone index to friendly conflict
errors and skip redundant GetByPhone when the phone is unchanged.

Not blocking: IAT test DB may need a one-off dedupe for index build;
phone uniqueness is per collection (users vs customers), not global.

internal/customer/errors.go

@@ -1,7 +1,42 @@
 package customer
 
-import "errors"
+import (
+	"errors"
 
-var (
-	ErrCustomerNotFound = errors.New("customer not found")
+	orm "tm/pkg/mongo"
 )
+
+var ErrCustomerNotFound = errors.New("customer not found")
+
+func mapCustomerWriteError(err error) error {
+	if err == nil || !orm.IsDuplicateKeyError(err) {
+		return err
+	}
+	switch {
+	case orm.DuplicateKeyMatchesField(err, "phone"):
+		return errors.New("customer with this phone number already exists")
+	case orm.DuplicateKeyMatchesField(err, "email"):
+		return errors.New("customer with this email already exists")
+	case orm.DuplicateKeyMatchesField(err, "username"):
+		return errors.New("customer with this username already exists")
+	default:
+		return err
+	}
+}
+
+func isCustomerConflictError(err error) bool {
+	if err == nil {
+		return false
+	}
+	switch err.Error() {
+	case "customer with this phone number already exists",
+		"customer with this email already exists",
+		"customer with this username already exists",
+		"company with this name already exists",
+		"company with this registration number already exists",
+		"company with this tax ID already exists":
+		return true
+	default:
+		return false
+	}
+}

internal/customer/handler.go

@@ -53,12 +53,7 @@ func (h *Handler) CreateCustomer(c echo.Context) error {
 
 	customer, err := h.service.Register(c.Request().Context(), form)
 	if err != nil {
-		if err.Error() == "customer with this email already exists" ||
-			err.Error() == "customer with this username already exists" ||
-			err.Error() == "customer with this phone number already exists" ||
-			err.Error() == "company with this name already exists" ||
-			err.Error() == "company with this registration number already exists" ||
-			err.Error() == "company with this tax ID already exists" {
+		if isCustomerConflictError(err) {
 			return response.Conflict(c, err.Error())
 		}
 		if strings.HasPrefix(err.Error(), "invalid company ID") || err.Error() == "invalid username format" {
@@ -127,12 +122,7 @@ func (h *Handler) UpdateCustomer(c echo.Context) error {
 		if err.Error() == "customer not found" {
 			return response.NotFound(c, "Customer not found")
 		}
-		if err.Error() == "customer with this email already exists" ||
-			err.Error() == "customer with this username already exists" ||
-			err.Error() == "customer with this phone number already exists" ||
-			err.Error() == "company with this name already exists" ||
-			err.Error() == "company with this registration number already exists" ||
-			err.Error() == "company with this tax ID already exists" {
+		if isCustomerConflictError(err) {
 			return response.Conflict(c, err.Error())
 		}
 		if strings.HasPrefix(err.Error(), "invalid company ID") {

internal/customer/service.go

@@ -156,6 +156,9 @@ func (s *customerService) Register(ctx context.Context, form *CreateCustomerForm
 	// Save to database
 	err = s.repository.Register(ctx, customer)
 	if err != nil {
+		if mapped := mapCustomerWriteError(err); mapped != err {
+			return nil, mapped
+		}
 		s.logger.Error("Failed to create customer", map[string]interface{}{
 			"error":    err.Error(),
 			"email":    form.Email,
@@ -424,6 +427,9 @@ func (s *customerService) Update(ctx context.Context, id string, form *UpdateCus
 	// Update in database
 	err = s.repository.Update(ctx, customer)
 	if err != nil {
+		if mapped := mapCustomerWriteError(err); mapped != err {
+			return nil, mapped
+		}
 		s.logger.Error("Failed to update customer", map[string]interface{}{
 			"error":       err.Error(),
 			"customer_id": id,