fix: align React runtime after package upgrade

[mrousavy]

Summary

• Pin React back to 19.2.3 across the workspace because 19.2.6 redboxed locally with Cannot read property 'useState' of null on RN 0.85.3.
• Regenerate bun.lock from a clean install so bun install --frozen-lockfile works on latest main.
• Refresh example/ios/Podfile.lock after pod install so the iOS example resolves the current Harness/Nitro pod versions.

No native Swift/Kotlin image behavior changes are included.

Local verification

• Cleaned local dependency/build/Metro caches before reproducing.
• bun install --frozen-lockfile
• RBENV_VERSION=3.4.9 bundle install in example/
• RBENV_VERSION=3.4.9 bundle exec pod install in example/ios/
• iOS Debug simulator build with Xcode 26.2 succeeded.
• Android Debug APK build succeeded with ./gradlew :app:assembleDebug --no-daemon --build-cache -PreactNativeArchitectures=arm64-v8a.
• Launched iOS app against Metro with reset cache; app loaded the harness screen and rendered the image.
• Launched Android app against Metro with reset cache; app loaded the harness screen and rendered the image.
• bun run lint-ci
• bun run build
• bun run typecheck

Harness behavior assertions may still be red; this PR is only meant to restore install/build/startup after the package upgrade and make the harness jobs actually run.