fix(staking): claimable rewards

[keyvankhademi]

This works for 0 reward, not sure if the endianness is correct because of it.

[vercel[bot]]

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Name	Status	Preview	Comments	Updated (UTC)
api-reference	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 11, 2024 8:21pm
staking-v2	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Sep 11, 2024 8:21pm

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| Name | Status | Preview | Comments | Updated (UTC) | | :--- | :----- | :------ | :------- | :------ | | **xc-admin-frontend** | ⬜️ Ignored ([Inspect](https://vercel.com/pyth-web/xc-admin-frontend/Cre7tg5Und6kV6dj7FvebD93cnNA)) | [Visit Preview](https://xc-admin-frontend-git-buffer-pyth-web.vercel.app) | | Sep 11, 2024 8:21pm |