feat(admin): improve tenant bulk import reporting with detailed results

- Backend: Enhanced 'ImportTenantsCSV' to return row-by-row details including action, status, and modified fields.
- Backend: Refactored 'upsertTenantCSVRecord' to detect and return specific modified fields (Name, Type, ParentID, Slug, Description, Config, Domains).
- Frontend: Added 'TenantImportDetail' and updated 'TenantImportResult' types.
- Frontend: Implemented a detailed results modal in 'TenantListPage' showing processing summary and row-level feedback for better transparency.

adminfront/src/lib/adminApi.ts

@@ -70,11 +70,22 @@ export type TenantUpdateRequest = {
   config?: Record<string, unknown>;
 };
 
+export type TenantImportDetail = {
+  row: number;
+  slug: string;
+  name: string;
+  success: boolean;
+  action: "created" | "updated" | "failed" | "skipped";
+  message: string;
+  modifiedFields?: string[];
+};
+
 export type TenantImportResult = {
   created: number;
   updated: number;
   failed: number;
   errors: string[];
+  details: TenantImportDetail[];
 };
 
 export type ApiKeySummary = {