bug: wallet address not checksum-validated before provider calls

[nanaf6203-bit]

Summary

fetchWalletBalance in src/utils/walletHelpers.ts accepts an address with no checksum or EIP-55 validation.

Affected area

src/utils/walletHelpers.ts and consumers: useWalletConnector, src/components/WalletConnectedView.tsx

Steps to reproduce / impact

Sending an invalid or mixed-case address may produce balance lookups against wrong accounts. Worse, in some chains EIP-55 checksum mismatch can indicate a typo-targeted phishing attempt.

Expected behaviour

Before reusing the address for any provider call, validate with viem getAddress or ethers utils.getAddress, which normalises and validates the checksum.

Acceptance criteria

• Introduce a helper assertValidAddress(addr: string): string in walletHelpers.ts.
• Throw on invalid input — convert caller error messages to user-safe copy.
• Add unit tests using well-known checksums and adversarial examples.

[khaylebfortune]

@khaylebfortune has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello Maintainer, I can fix this issue.

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[Penielka]

@Penielka has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

can i be assigned this

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[drips-wave]

This issue has been completed by @Penielka as part of the Stellar Wave Program's 6th Wave 🥳

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