Add global and route-level error boundaries with production error logging

[Tomoya0k]

Summary

This PR adds a global recovery UI for unhandled React errors and route-level error boundaries for major App Router sections.

What changed

• added app/global-error.tsx to handle unhandled app-level React errors
• added a friendly recovery screen with:
  • user-friendly message
  • developer-only technical details in development
  • Try again and Reload page actions
  • issue reporting link
• added production error logging to .data/error-log.json
• added POST /api/errors/report to persist client-reported errors on the server
• added route-level error boundaries for:
  • /map
  • /leaderboard
  • /admin
• extracted shared route error UI into a reusable component to avoid duplication
• extracted client-side error reporting into a shared utility
• updated error log entry IDs to use crypto.randomUUID()

Notes

• the original issue mentioned /registry, but that route does not exist in the current repo state
• /admin was used instead as a major real route with equivalent importance
• the global error handling is implemented using Next.js App Router's native app/global-error.tsx mechanism

Closes #210

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud