fix: normalize ReactNative URLS

[wenfix]

Explanation

• React Native apps can provide custom-scheme URLs (e.g. react-native-playground://) as dapp.url, which breaks downstream wallet RPC middleware that calls new URL() expecting http(s) schemes
• Adds normalizeNativeUrl() helper in setupDappMetadata() that converts non-http(s) URLs to https://<sanitized-scheme>.rn.dapp.local on RN platforms
• Preserves the original URL in a new nativeScheme field on DappSettings

Testing

Unit tests

cd packages/connect-multichain && yarn vitest run src/multichain/utils/index.test.ts

Manual (React Native playground)

1. cd playground/react-native-playground && cp .env.example .env (add Infura key)
2. yarn ios or yarn android
3. Use the Wagmi tab to connect — it passes react-native-playground:// as dapp.url
4. Verify console log: Normalizing dapp URL for React Native: "react-native-playground://" -> "https://react-native-playground.rn.dapp.local"
5. Connection should succeed without RPC middleware crash

References

Fixes WAPI-1134

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes