fix(midi): route MIDI live via masterBus, fix media explorer drag, add action logging

- TrackInstrument: gate native live path (SF/VSTi WASAPI bridge bypassed
  masterBus -> mastering FX + main out VU dead). Fallback to SonicSF WASM
  through masterBus.input; native kept for offline render only.
- MEDIA_LIBRARY_SAMPLES: rename MIDI_Loop_02_Bass/03_Lead/05_Bass to match
  actual /static/midi files (drag was 404 -> parse error).
- Add SonicAppLogger (console + POST /api/v1/logs) wired to: instrument load
  error, VSTi autosample fail, MIDI item -> mastering fx chain, play -> main
  out, drag MIDI errors (media explorer + window explorer).
- Add backend /api/v1/logs endpoint (server-side log, no DB).

app/main.py

@@ -21,6 +21,7 @@ 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.api.v1.logs import router as logs_router
 from app.core.auth import seed_admin
 from app.core.soundfont_scanner import SoundFontAutoScanner
 
@@ -114,6 +115,7 @@ 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.include_router(logs_router, prefix="/api/v1/logs", tags=["logs"])
 
 
 @app.get("/health")