Move native code from native/ to Expo-compatible layout with android/
and ios/ at package root. Add Android JNI bridge (OnLoad.cpp,
ExpoSalviumCryptoModule.java, ExpoSalviumCryptoPackage.java).
Prebuilt binaries now go in prebuilt/ instead of native/lib/.
Test fixes:
- wallet-sync: update stale DEFAULT_BATCH_SIZE assertion (10 -> 100)
- bulletproofs+: fix hashToPoint -> hashToPointMonero rename in test,
fix serializeProof to include V array matching parseProof format
- transaction-builder: expect 2 outputs for exact-amount tx (zero-change
output is always added for privacy)