Add Android deep-link E2E coverage

[ejones23]

Summary

• add Expo development-client support without committing permanent store identifiers
• add an automated Android incoming-link to rank to submit to results milestone scenario
• document Expo Go and custom rankedchoices:// development-build invocation
• preserve the canonical /ballot/[key] route

Verification

• Android API 36 Expo Go cold-start E2E passed
• installed development build E2E passed through rankedchoices://ballot/pizza
• mobile tests, typecheck, lint, and static export
• 188 legacy JavaScript tests and 217 PHP tests
• live PHP/MySQL contract suite and production Vite build

The development build used disposable com.rankedchoices.dev; permanent Apple and Android identifiers remain a product decision.

_{Stack created with GitHub Stacks CLI.}

[DavidMoritz]

Great finishing touch on the stack, Emmanuel! The env-var-driven app.config.js is the right call — keeping store identifiers out of the repo while making dev builds seamless. And the E2E script is clever: using content-desc (accessibility labels) for UI targeting validates accessibility while also being resilient to visual changes. The synchronous Atomics.wait sleep is a nice touch for a script that's synchronous by design.

Really appreciate you documenting the Expo Go vs custom-scheme dev flows in the README too — that's going to save a lot of onboarding time.

Thank you as always, Emmanuel. This entire 5-PR stack is a masterclass in incremental, well-tested mobile development. Your volunteer work on this project is extraordinary and we're so lucky to have you! 🚀