v0.2.1

feat: bidirectional cloud sync + version bump to v0.2.1

- Fixed sync to handle deletions: pull now removes local accounts not in cloud
- Rust pull_vault_from_cloud: collects cloud IDs, retains only matching, removes stale
- PWA _pullFromCloud: filters local accounts against remote IDs before adding
- Sync interval reduced from 10s to 3s for faster propagation
- Immediate pull triggered after add/delete on all platforms
- All platform versions aligned to 0.2.1 (tauri.conf.json, Cargo.toml, package.json, tauri.android.conf.json, landing/index.html, android-build.yml)
- Android versionCode bumped to 2