Add single-command installation: install.sh, Makefile, frontend build hook

- hatch_build.py: custom hatchling build hook that compiles the React
  frontend (npm ci + build) when frontend/dist is missing or stale, so
  'uv tool install git+https://gitea.zephyre.one/Pakobbix/nvcurve.git'
  works as a single command
- install.sh: curl|bash installer (checks prerequisites, auto-installs uv,
  clones and installs)
- Makefile: dev targets (frontend, install, dev, test, clean)
- README/docs: document the one-liner, clone, and direct-git installs

Makefile

@@ -0,0 +1,29 @@
+# NVCurve — developer convenience targets.
+#
+# End users don't need make: run ./install.sh (see README "Installation").
+
+UV  ?= uv
+NPM ?= npm
+
+.PHONY: help frontend frontend-dev install dev test clean
+
+help: ## Show available targets
+	@grep -E '^[a-zA-Z_-]+:.*?## ' $(MAKEFILE_LIST) | awk 'BEGIN {FS = ":.*?## "}; {printf "  \033[36m%-15s\033[0m %s\n", $$1, $$2}'
+
+frontend: ## Build the React frontend into frontend/dist
+	cd frontend && $(NPM) ci && $(NPM) run build
+
+frontend-dev: ## Run the Vite dev server (hot reload)
+	cd frontend && $(NPM) run dev
+
+install: ## Install nvcurve as a uv tool (builds frontend if missing/stale)
+	$(UV) tool install --force .
+
+dev: ## Create/refresh the dev environment (uv sync)
+	$(UV) sync
+
+test: ## Run the test suite
+	$(UV) run python tests/test_security.py
+
+clean: ## Remove build artifacts
+	rm -rf frontend/dist frontend/node_modules