chore: remove Sentry.io entirely

We no longer use Sentry. Removed:
- @sentry/react + @sentry/vite-plugin (package.json + lockfile)
- Sentry.init in index.tsx and the VITE_SENTRY_DSN env (.env.production)
- @sentry/vite-plugin + the SENTRY_AUTH_TOKEN sourcemap-upload path in
  vite.config.js (sourcemap now always false) and the CI env var
- Sentry.ErrorBoundary in App.tsx -> react-error-boundary's ErrorBoundary with a
  folds-native fallback (Box/Text/Button + config tokens), which also resolves
  the native-cinny audit's raw-#hex/#5865f2 fallback finding.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitea/workflows/ci.yml

@@ -45,7 +45,6 @@ jobs:
         run: npm run build
         env:
           NODE_OPTIONS: '--max_old_space_size=4096'
-          SENTRY_AUTH_TOKEN: ${{ secrets.SENTRY_AUTH_TOKEN }}
           VITE_APP_VERSION: ${{ github.sha }}
 
       # ── Quality checks (informational — pre-existing issues exist) ───────