chore: initialize the Go module and repository scaffolding

Add the Go module definition and lockfile, editor and ignore rules, and a Makefile with build, test, vet, install, and man targets. The version is injected at build time with -ldflags.

Makefile

@@ -0,0 +1,40 @@
+BINARY  := lazyntfy
+PREFIX  ?= $(HOME)/.local
+BINDIR  ?= $(PREFIX)/bin
+MANDIR  ?= $(PREFIX)/share/man/man1
+VERSION ?= $(shell git describe --tags --always --dirty 2>/dev/null | sed 's/^v//' | grep . || echo 0.1.0)
+TOPIC   ?= alerts
+
+LDFLAGS := -X main.version=$(VERSION)
+
+.PHONY: build install uninstall test vet fmt run man clean
+
+build:
+	go build -ldflags "$(LDFLAGS)" -o $(BINARY) ./cmd/lazyntfy
+
+install: build
+	mkdir -p "$(BINDIR)" "$(MANDIR)"
+	install -m 755 $(BINARY) "$(BINDIR)/$(BINARY)"
+	install -m 644 man/lazyntfy.1 "$(MANDIR)/lazyntfy.1"
+
+uninstall:
+	rm -f "$(BINDIR)/$(BINARY)" "$(MANDIR)/lazyntfy.1"
+
+man:
+	mkdir -p "$(MANDIR)"
+	install -m 644 man/lazyntfy.1 "$(MANDIR)/lazyntfy.1"
+
+test:
+	go test ./...
+
+vet:
+	go vet ./...
+
+fmt:
+	gofmt -w .
+
+run: build
+	./$(BINARY) $(TOPIC)
+
+clean:
+	rm -f $(BINARY)