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

Makefile

@@ -0,0 +1,20 @@
+BINDIR ?= $(HOME)/.local/bin
+
+.PHONY: build install uninstall test clippy
+
+build:
+	cargo build --release
+
+install: build
+	install -Dm755 target/release/vois $(BINDIR)/vois
+	@echo "installed: $(BINDIR)/vois"
+	@echo "make sure $(BINDIR) is on your PATH, then just run: vois"
+
+uninstall:
+	rm -f $(BINDIR)/vois
+
+test:
+	cargo test --bin vois
+
+clippy:
+	cargo clippy --all-targets -- -D warnings