Add mobile/iOS conversion spec (PK-117)

[parvezk]

Summary

Adds a comprehensive specification document at docs/MOBILE_CONVERSION_SPEC.md that evaluates approaches for converting the Tranche web app to a mobile/iOS application.

What's Included

The spec covers:

• Current architecture inventory — detailed analysis of the existing Next.js 14 / React 18 / Zustand / Tailwind stack, all features, API routes, and server-side dependencies
• Four approach evaluations:
  • Capacitor (recommended) — wrap existing web app in native iOS WebView shell; ~95% code reuse
  • React Native / Expo — rewrite UI with native components, share business logic; ~45% code reuse
  • Flutter — full rewrite in Dart; ~0% code reuse
  • Electron — desktop only, does not target iOS/mobile
• Detailed migration plan for Capacitor path — 6 phases covering API proxy extraction, static export, Capacitor setup, mobile UX adaptations, persistence, and App Store preparation
• Touch interaction redesign — hover→tap conversions, bottom sheet for performance data, responsive card layout for positions
• Native feature integrations — Share sheet, Haptics, Status Bar, Splash Screen, Keyboard handling
• Risk assessment and mitigation strategies
• Decision matrix comparing all four approaches across 10 criteria

Resolves

Linear issue PK-117: "Develop high-level spec to convert this web app to mobile/iOS app using Electron or Flutter"

Linear Issue: PK-117

  

[linear]

PK-117 Develop high-level spec to convert this to web app to mobile/iOS app using Electron or Flutter