build: add Makefile wrapping npm scripts

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Makefile

@@ -0,0 +1,32 @@
+.PHONY: help install dev build preview start typecheck test test-watch clean
+
+help: ## Show this help
+	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) | \
+		awk 'BEGIN {FS = ":.*?## "}; {printf "  \033[36m%-12s\033[0m %s\n", $$1, $$2}'
+
+install: ## Install dependencies
+	npm install
+
+dev: ## Run the app in development mode
+	npm run dev
+
+build: ## Build the app
+	npm run build
+
+preview: ## Preview the built app
+	npm run preview
+
+start: ## Start the previewed app
+	npm run start
+
+typecheck: ## Run TypeScript type checking
+	npm run typecheck
+
+test: ## Run the test suite once
+	npm run test
+
+test-watch: ## Run tests in watch mode
+	npm run test:watch
+
+clean: ## Remove build output and dependencies
+	rm -rf out dist node_modules