refactor: track background tasks in application lifecycle and clean up codebase

tests/test_effects.py

@@ -60,11 +60,10 @@ class TestAudioEffects(unittest.TestCase):
         fx = ToasterEffect(bit_depth=5, downsample=6)
         pcm = struct.pack("<hh", 12345, -23456)
         out = fx.process(pcm)
-        l, r = struct.unpack("<hh", out)
+        left, right = struct.unpack("<hh", out)
         # Low 11 bits are zeroed due to 5-bit quantization
-        self.assertEqual(l & 0x07FF, 0)
-        self.assertEqual(r & 0x07FF, 0)
-
+        self.assertEqual(left & 0x07FF, 0)
+        self.assertEqual(right & 0x07FF, 0)
 
     def test_pipeline_chains_multiple_effects_and_applies_volume(self):
         pipeline = AudioEffectsPipeline(create_default_effects())