Refactor: Enforce type safety, fix close deadlock, implement assignee restrictions and notify admin fallbacks

tests/Feature/ImportCskhTest.php

@@ -116,11 +116,11 @@ test('cskh import command processes rows correctly in dry run and active modes',
     
     $handover = Handover::where('product_id', $productA->id)->first();
     expect($handover)->not->toBeNull();
-    expect($handover->handover_date)->toBe('2026-01-01');
+    expect($handover->handover_date->format('Y-m-d'))->toBe('2026-01-01');
     
     $contract = Contract::where('product_id', $productA->id)->first();
     expect($contract)->not->toBeNull();
-    expect($contract->type)->toBe('lease'); // type is a string 'lease'
+    expect($contract->type->value)->toBe('lease'); // type is ContractType enum
 
     // Clean up temporary file
     @unlink($csvPath);