Fix: StarEffect audio dependency

[robertlipe]

Removes strict dependency on ENABLE_AUDIO and VU > 0 in StarEffect. Allows stars to spawn in silence/no-mic configurations using base probability logic.

Previously, a build without AUDIO would render options into the effects array for RGB+Rainbow stars, but they woiuldn't emit pixels. If your device was on auto-play, you'd just get a few minutes of a dark screen while those effects hogged the spotlight without actually making blinkies.