T15: drop WebAudio master for tracks - native master gain + track gain/pan IPC (SF/VST2/VST3 bridges), NativeAudioService + /api/v1/native router, native-first TrackInstrument, test matrix 8 passed

app/main.py

@@ -20,6 +20,7 @@ from app.api.v1.plugins import router as plugins_router
 from app.api.v1.media import router as media_router
 from app.api.v1.system import router as system_router
 from app.api.v1.presets import router as presets_router
+from app.api.v1.native import router as native_router
 from app.core.auth import seed_admin
 from app.core.soundfont_scanner import SoundFontAutoScanner
 
@@ -112,6 +113,7 @@ app.include_router(plugins_router, prefix="/api/v1/plugins", tags=["plugins"])
 app.include_router(media_router, prefix="/api/v1/media", tags=["media"])
 app.include_router(system_router, prefix="/api/v1/system", tags=["system"])
 app.include_router(presets_router, prefix="/api/v1/presets", tags=["presets"])
+app.include_router(native_router, prefix="/api/v1/native", tags=["native"])
 
 
 @app.get("/health")