CAudio::~CAudio() waited on MaoscBufferCopied(KErrAbort) to set
EStateDone, but that callback can never fire once the active scheduler
loop has exited, deadlocking every close.
- StopThread() before iStream->Stop() in ~CAudio()
- Force iState = EStateDone instead of waiting on a dead callback
- Add 5s timeout to AudioIsReady() poll in E32Main()
- Fix CleanupStack LIFO pop order (mainApp before gRenderer)
- Change active object priority from EPriorityLow to EPriorityStandard
- Process all events in batch before SDL_AppIterate() to reduce input lag
- Remove redundant SDL_PumpEvents() call (already done by SDL_PollEvent)
- Move clean-up logic into ShutdownApp() helper function
