[Sensei-Victor]

Summary

Previously, KNOWN_TOKEN_METADATA mapped the native XLM contract address (CDLZFC3SYJYDZT7K67VZ75HPJVIEUVNIXF47ZG2FB2RMQQVU2HHGCYSC on testnet) to USDC. Consequently, any native XLM stream rendered as USDC, and the native token selector was mismatched.

This change:

• Maps the native contract ID for the configured network to Stellar Lumen / XLM dynamically using nativeAssetContractId(config.networkPassphrase).
• Removes the hardcoded USDC entry from fallback metadata.
• Separates the useTokenMetadata and useTokensMetadata React hooks into hooks/use-token-metadata.ts to decouple the React lifecycle from RPC simulation helpers and enable clean test mocking.
• Updates tests and mock fixtures in format, stream search, and total calculations to use the native asset contract for XLM and realistic mock addresses for other tokens.
• Cleans up unused imports and hooks effect dependencies to ensure lint and typecheck pass cleanly.

Linked issue

Closes #503

What was tested

• Ran npm test covering all 103 test suites (955 tests passing), including token-display, token-metadata, format, stream-search, and stream-total.
• Ran npm run lint and npm run typecheck cleanly with 0 errors and 0 warnings.
• Ran npm run build validating production compilation and static page generation.

Checklist

• npm test passes
• npm run typecheck passes
• npm run lint passes
• Tested locally in the browser (where the change touches UI)