Run as 'vois': install via make, config file, Auto-Tune, more presets, custom chains

- 'vois' installs to PATH (make install) and works with no flags:
  auto device selection (pipewire/pulse/default) and 48 kHz default
- ~/.config/vois/config.toml for defaults + custom preset chains (serde)
- Auto-Tune pitch correction (snap to nearest semitone, smoothed)
- 5 new presets: Chipmunk, Helium, Vader, Telephone, Growl (17 total)
- --pitch-correct flag, --no-virtual-mic to disable the default virtual mic
- no dead-code allowances; clippy/fmt/tests clean

Cargo.toml

@@ -14,7 +14,9 @@ hound = "3"
 ratatui = "0.28"
 ringbuf = "0.4"
 rustfft = "6"
+serde = { version = "1.0.229", features = ["derive"] }
 signal-hook = "0.3"
+toml = "0.8"
 
 [profile.release]
 opt-level = 3