Implement SMB 3.x Lease support Phase 4

- CLOSE handler unregister lease_key from LeaseManager
- Extract lease_key from Open struct before close

All 229 tests pass.

vendor/smb-server/src/handlers/close.rs

@@ -44,6 +44,7 @@ pub async fn handle(
     let path = open.last_path.clone();
     let delete_on_close = open.delete_on_close;
     let oplock_level = open.oplock_level;
+    let lease_key = open.lease_key.clone(); // Phase 4: for lease unregister
     let want_attrs = req.flags & FLAG_POSTQUERY_ATTRIB != 0;
     drop(open);
 
@@ -52,6 +53,11 @@ pub async fn handle(
         server.oplock_manager.unregister(&path, &req.file_id).await;
     }
     
+    // Phase 4: Unregister from LeaseManager if lease was granted
+    if let Some(lease_key) = lease_key {
+        server.lease_manager.unregister(&lease_key).await;
+    }
+
     // Phase 7: Clear all byte-range locks for this file
     server.lock_manager.clear(&req.file_id).await;