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/middleware/audit_middleware.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"log/slog"
+	"maps"
 	"reflect"
 	"sync"
 	"time"
@@ -28,7 +29,7 @@ func isNil(i any) bool {
 		return true
 	}
 	v := reflect.ValueOf(i)
-	return v.Kind() == reflect.Ptr && v.IsNil()
+	return v.Kind() == reflect.Pointer && v.IsNil()
 }
 
 // AuditMiddleware provides comprehensive audit logging for write requests by default.
@@ -153,10 +154,8 @@ func AuditMiddleware(config AuditConfig) fiber.Handler {
 				for key, value := range v {
 					details[key] = value
 				}
-			case map[string]interface{}:
-				for key, value := range v {
-					details[key] = value
-				}
+			case map[string]any:
+				maps.Copy(details, v)
 			}
 		}
 		if skipTimeline, ok := c.Locals("auth_timeline_skip").(bool); ok && skipTimeline {