Security/stellar address validation

[DevALVIN-24]

closes #494

PR Description

📌 Description

This PR resolves a security/UI vulnerability where AddressDisplay and explorer link helpers accepted arbitrary strings. A malformed or attacker-controlled value would be rendered directly into a Stellar Expert explorer href.

We now enforce standard Stellar StrKey format validation (specifically validating standard Ed25519 Account and Contract lengths, prefixes, and valid base32 charset usage) before creating explorer links. Invalid addresses are marked visually with a warning strike-through style and specific aria-labels, and explorer links are hidden for them. The user can still copy the address string verbatim if they need to debug the malformed key.

🎯 Changes Made

• New Utility: Added isValidStellarAddress in src/utils/stellarAddress.ts to strictly validate G and C keys (56 length + standard RFC4648 Base32 alphabet constraints).
• Guarded Components: Updated AddressDisplay.tsx to utilize this function. Visually strike-throughs and labels invalid addresses with a warning message, whilst hiding the explorer hyperlink.
• Guarded Helpers: Refactored getExplorerAccountUrl and contractExplorerUrl inside src/utils/explorer.ts to return an empty string when the supplied address fails validation checks.
• Tests Implemented:
  • Added full test coverage for the isValidStellarAddress utility handling all major edge cases (wrong lengths, invalid prefix, lower-case, bad padding).
  • Extended AddressDisplay.test.tsx to handle testing of invalid marking rendering and assuring explorer links are conditionally hidden.
• Documentation: Created design-system/documentation/address-validation.md to reflect the new address formatting rules and implementations for developers.

✅ Testing & Validation

• Ran the testing suite ensuring full compliance and 100% line and branch coverage on the specifically modified functions/components. Tested edge cases include valid G/C keys, empty strings, invalid characters (e.g. 1 and 0), and invalid lengths.

---

[drips-wave]

@DevALVIN-24 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[DevALVIN-24]

okay

[1nonlypiece]

stellar address validation tightened up, good. merged