feat(user): support fixed UUID registration and enhance bulk import results

- Added support for fixed UUIDs during bulk registration (Search-first + ExternalID mapping)
- Implemented idempotency and visibility restoration for soft-deleted users
- Enhanced bulk upload UI to show 'New/Updated/Unchanged' status and modified fields
- Added logic to reclaim identifiers (login_id) from colliding records
- Added frontend E2E and backend unit tests for UUID integrity and conflict handling
- Fixed i18n, formatting, and mock tests to satisfy code-check
- Applied 'go fix' for 'omitzero' tags and general Go standards

backend/internal/handler/auth_handler_profile_cache_test.go

@@ -5,6 +5,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"maps"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -33,7 +34,7 @@ func (r *recordingUpdateMeUserRepo) UpdateUserLoginIDs(ctx context.Context, user
 func TestUpdateMe_InvalidatesProfileCacheForTokenSession(t *testing.T) {
 	token := "token-abc"
 	identityID := "user-1"
-	traits := map[string]interface{}{
+	traits := map[string]any{
 		"email":           "qa@example.com",
 		"name":            "QA User",
 		"phone_number":    "+821012345678",
@@ -51,8 +52,8 @@ func TestUpdateMe_InvalidatesProfileCacheForTokenSession(t *testing.T) {
 			if r.Header.Get("X-Session-Token") != token {
 				return httpResponse(r, http.StatusUnauthorized, `{"error":"invalid token"}`), nil
 			}
-			return httpJSONAny(r, http.StatusOK, map[string]interface{}{
-				"identity": map[string]interface{}{
+			return httpJSONAny(r, http.StatusOK, map[string]any{
+				"identity": map[string]any{
 					"id":     identityID,
 					"traits": traits,
 				},
@@ -62,14 +63,12 @@ func TestUpdateMe_InvalidatesProfileCacheForTokenSession(t *testing.T) {
 			r.URL.Path == "/admin/identities/"+identityID &&
 			r.Method == http.MethodPut:
 			var payload struct {
-				Traits map[string]interface{} `json:"traits"`
+				Traits map[string]any `json:"traits"`
 			}
 			if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
 				return httpResponse(r, http.StatusBadRequest, `{"error":"invalid body"}`), nil
 			}
-			for k, v := range payload.Traits {
-				traits[k] = v
-			}
+			maps.Copy(traits, payload.Traits)
 			return httpResponse(r, http.StatusOK, `{"ok":true}`), nil
 		}
 
@@ -93,7 +92,7 @@ func TestUpdateMe_InvalidatesProfileCacheForTokenSession(t *testing.T) {
 	getResp1, err := app.Test(getReq1, -1)
 	require.NoError(t, err)
 	require.Equal(t, http.StatusOK, getResp1.StatusCode)
-	var profile1 map[string]interface{}
+	var profile1 map[string]any
 	require.NoError(t, json.NewDecoder(getResp1.Body).Decode(&profile1))
 	require.Equal(t, "Old Dept", profile1["department"])
 
@@ -121,7 +120,7 @@ func TestUpdateMe_InvalidatesProfileCacheForTokenSession(t *testing.T) {
 	getResp2, err := app.Test(getReq2, -1)
 	require.NoError(t, err)
 	require.Equal(t, http.StatusOK, getResp2.StatusCode)
-	var profile2 map[string]interface{}
+	var profile2 map[string]any
 	require.NoError(t, json.NewDecoder(getResp2.Body).Decode(&profile2))
 	require.Equal(t, "New Dept", profile2["department"])
 }
@@ -129,7 +128,7 @@ func TestUpdateMe_InvalidatesProfileCacheForTokenSession(t *testing.T) {
 func TestUpdateMe_SyncsLocalReadModelFields(t *testing.T) {
 	token := "token-sync"
 	identityID := "user-sync"
-	traits := map[string]interface{}{
+	traits := map[string]any{
 		"email":           "sync@example.com",
 		"name":            "Old Name",
 		"phone_number":    "+821012345678",
@@ -148,8 +147,8 @@ func TestUpdateMe_SyncsLocalReadModelFields(t *testing.T) {
 			if r.Header.Get("X-Session-Token") != token {
 				return httpResponse(r, http.StatusUnauthorized, `{"error":"invalid token"}`), nil
 			}
-			return httpJSONAny(r, http.StatusOK, map[string]interface{}{
-				"identity": map[string]interface{}{
+			return httpJSONAny(r, http.StatusOK, map[string]any{
+				"identity": map[string]any{
 					"id":     identityID,
 					"traits": traits,
 				},
@@ -159,14 +158,12 @@ func TestUpdateMe_SyncsLocalReadModelFields(t *testing.T) {
 			r.URL.Path == "/admin/identities/"+identityID &&
 			r.Method == http.MethodPut:
 			var payload struct {
-				Traits map[string]interface{} `json:"traits"`
+				Traits map[string]any `json:"traits"`
 			}
 			if err := json.NewDecoder(r.Body).Decode(&payload); err != nil {
 				return httpResponse(r, http.StatusBadRequest, `{"error":"invalid body"}`), nil
 			}
-			for k, v := range payload.Traits {
-				traits[k] = v
-			}
+			maps.Copy(traits, payload.Traits)
 			return httpResponse(r, http.StatusOK, `{"ok":true}`), nil
 		}
 
@@ -187,7 +184,7 @@ func TestUpdateMe_SyncsLocalReadModelFields(t *testing.T) {
 	app := fiber.New()
 	app.Put("/api/v1/user/me", h.UpdateMe)
 
-	updateBody, _ := json.Marshal(map[string]interface{}{
+	updateBody, _ := json.Marshal(map[string]any{
 		"name":       "New Name",
 		"phone":      "01087654321",
 		"department": "New Dept",