Add env vars, EAS builds, and architecture details for engage-native

[mintlify]

Summary

Syncs documentation with the initial commit of d-sports-engage-native (PR d-sports-ecosystem/d-sports-engage-native#17).

Trigger repo changes

• d-sports-engage-native commit 08ac7b3: "chore: UI polish, accessibility improvements, and code cleanup" — initial commit adding 410 files (full project).

Doc pages updated

repositories/d-sports-engage-native.mdx

• Added environment variables table documenting all required EXPO_PUBLIC_* keys
• Added EAS build profiles table (development, preview, staging, production) with common build commands
• Added CI/CD section covering the GitHub Actions OTA update workflow
• Updated "What changed since last docs sync" to reflect accessibility, tab bar, modular architecture, and EAS additions

repositories/d-sports-engage-native/architecture.mdx

• Added modular architecture section (thin render shells, external stylesheets, one component per file, centralized types)
• Added tab bar architecture section (iOS NativeTabs vs Android/web PillTabBar, shared config)
• Added accessibility architecture section (AccessibilityContext, VoiceOver, larger text, reduced motion, high contrast)
• Expanded state management and API client sections with specific file references
• Added platform-specific behavior details for iOS, Android, and web