fix(mobile): restore OpenPanel event delivery

[sjungwon03]

Summary

• Replace the Expo-incompatible OpenPanel React Native adapter with the platform-neutral OpenPanel core client.
• Retain the public write key, allow-listed app://openscene Origin, payload filter, and usage-reporting switch.
• Remove the adapter dependency that throws before any event can be sent on the Expo 57 Android runtime.

Verification

• Mobile typecheck passed.
• Mobile analytics test passed: 20 tests.
• Metro Android production bundle succeeded.

Local Android packaging was attempted after a clean but failed in the existing expo-modules-core Dex transform. Exact-HEAD CI will build on a clean runner.

Closes #293

[sjungwon03-ai]

Reviewed on the exact head. The pinned, dependency-free OpenPanel core client preserves the lazy load, allow-listed Origin, and final send-seam payload filter while removing the Expo-incompatible adapter. The complete direct-head mobile CI suite passed, including Android assembly and the iOS simulator build.