Deploying larger compiled packages can fail during base64 encoding

## Summary

Deploying a compiled contract can fail before `useDeploy()` is called when the compiled package is large enough.

`ContractList` converts `contract.packageBytes` to base64 with:

```ts
btoa(String.fromCharCode(...contract.packageBytes))
```

Spreading a large `Uint8Array` into `String.fromCharCode()` is limited by the JavaScript engine's maximum argument count. Once the compiled package crosses that threshold, the click handler throws synchronously with `RangeError: Maximum call stack size exceeded` and the deploy flow never starts.

## Repro

This is the same conversion pattern used by the deploy button:

```sh
node -e "const b=new Uint8Array(200000); String.fromCharCode(...b)"
```

It fails with:

```text
RangeError: Maximum call stack size exceeded
```

## Impact

A contract can compile successfully and still be impossible to deploy from the UI solely because its `.masp` package is too large for the spread call. The deploy hook already accepts base64, so this is only an encoding issue in the UI boundary.

## Suggested fix

Encode the `Uint8Array` in chunks, or move a safe `uint8ArrayToBase64()` helper into a shared utility and use it from `ContractList`.

contract.packageBytes が base64 に変換される ContractList コンポーネントを確認してください。問題は String.fromCharCode(...contract.packageBytes) の使用にあります。大きな Uint8Array を安全に base64 エンコードするためのユーティリティ関数を、共有の utils ファイルなどで探すか作成してください。大きなパッケージのデプロイをシミュレートして修正をテストします。

索引モデルが issue の本文から書いたものです。