perf(admin): implement server-side search and virtualization for tenant list

- Backend: Added 'search' parameter to TenantRepository and TenantService.
- Backend: Updated all Tenant list calls to support searching.
- Backend: Enhanced UserRepository.List to support cursor-based pagination and search.
- Frontend: Switched TenantListPage to use useInfiniteQuery for lazy loading.
- Frontend: Implemented list virtualization in TenantHierarchyView using @tanstack/react-virtual.
- Frontend: Added server-side search with debouncing (useDeferredValue).
- Fixed various Go compilation errors caused by method signature changes.

backend/internal/handler/auth_handler.go

@@ -629,7 +629,7 @@ func (h *AuthHandler) GetActiveTenants(c *fiber.Ctx) error {
 	}
 
 	// 3. List and Filter Tenants
-	tenants, _, err := h.TenantService.ListTenants(c.Context(), 1000, 0, "")
+	tenants, _, err := h.TenantService.ListTenants(c.Context(), 1000, 0, "", "")
 	if err != nil {
 		return errorJSON(c, fiber.StatusInternalServerError, "Failed to fetch tenants")
 	}