feat(expo-example): add Passkey auth and test on Android

[andrascodes]

This PR is part of a stack created with Aviator. feat(expo-example): add export wallet on mobile #168 feat(expo-example): configure and add magic link login #142 fix(expo-example): add EAS local build config and fix HMR bug with secureStoreStamper #141 feat(expo-example): migrate to expo-router #131 feat(react): enable OAuth in React Native #80 ➡️ feat(expo-example): add Passkey auth and test on Android #124 main

Closes FS-1928, FS-1999

The main purpose of the PR is setting up the Android build in a way that we can accomplish a PasskeyAuth on Android Emulator. Since the PasskeyStamper is already committed to the expo-example repo I just added a component to the app to trigger the Passkey register/login (using the hook) - no other changes were needed to make it work.

Changes explained:

• assetlinks.json: a static json file deployed at zerodev-expo-example.vercel.app, this connects the domain to the app for App Links and Passkeys both
• debug.keystore: the app build needs to be signed with a key and the resulting fingerprint is added to the assetlinks.json file this makes the connection between the app and the domain - this keystore is committed so every contributor can use it to sign the builds and test Passkeys and App Links
• withDebugKeystore.js: expo plugin applied so the Android prebuilds use the debug.keystore instead of the one on the contributor's machine
• Separated the wagmi.config files for platform specific ones
• eas.json: setting up the EAS CLI for creating a local APK build that can be installed on a physical device or emulator, credentials.json is what this is looking for to get the signing credentials for the build
  • So there's the Expo Development build that you get by running pnpm android and a local APK build you get by running pnpm dlx eas-cli build --platform android --local --profile preview. Both will use the committed debug.keystore for signing so Passkeys and App Links will work on both (both looks at the zerodev-expo-example.vercel.app domain for verification).

[SahilVasava]

If Expo ever changes the prebuild template (different quote style, extra config block, etc.), this replace becomes a no-op and signing silently falls back to ~/.android/debug.keystore per machine — passkeys then break with no useful error.

Worth asserting the replacement actually happened:

const before = config.modResults.contents
config.modResults.contents = before.replace(
  "storeFile file('debug.keystore')",
  "storeFile file('../../credentials/debug.keystore')",
)
if (config.modResults.contents === before) {
  throw new Error("withDebugKeystore: storeFile pattern not found in build.gradle — Expo prebuild template may have changed")
}

Fails loud at prebuild time instead of silently breaking passkeys at runtime.

[SahilVasava]

Solid. One nit on the prebuild plugin to fail loud instead of silent.