build(#83): NeurophoneService → generated Java Service shim → JNI

[hyperpolymath]

Sub-task of #83 (gossamer migration).

Replace NeurophoneService.kt (foreground Service) with a minimal generated Java Service shim under the exempt gen/ dir that JNIs into Rust. A webview shell (gossamer) does not host Android Services, so the shim is the JVM-bytecode surface that must remain. Business logic lives in crates/neurophone-android.

Parallelizable after the gossamer Android scaffolding.