Fix missing n3 attribute and async function issue

- Add missing self.n3 = 1 attribute to MidiHandler initialization
- Fix update_rgb async function to properly yield control with await asyncio.sleep(0)
- Resolves TypeError about expecting coroutine but getting None
- Application now working properly with buttons and dials functional

src/midi.py

@@ -54,6 +54,7 @@ class MidiHandler:
         # Raw CC-driven parameters (0-127)
         self.n1 = 10
         self.n2 = 10
+        self.n3 = 1
         # Additional knobs (CC38-45)
         self.knob1 = 0
         self.knob2 = 0