chore(devops): docker-compose dev + prod, Dockerfiles, nginx, Makefile

- backend/Dockerfile: Python 3.12 slim, non-root user, WeasyPrint system deps
- backend/Dockerfile.dev: dev variant with hot-reload support
- frontend/Dockerfile: Node 20 alpine build + nginx:alpine serve
- frontend/nginx.conf: SPA routing + /api proxy to backend:8000
- docker-compose.yml: production with healthcheck
- docker-compose.dev.yml: dev with volume mounts and hot-reload
- Makefile: dev, build, up, down, logs, migrate, test, shell, prod targets
- .dockerignore for backend and frontend

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Makefile

@@ -0,0 +1,45 @@
+.PHONY: dev build up down logs migrate test shell-backend shell-frontend seed backup prod-build prod-up
+
+# Development
+dev:
+	docker compose -f docker-compose.dev.yml up
+
+build:
+	docker compose -f docker-compose.dev.yml build
+
+up:
+	docker compose -f docker-compose.dev.yml up -d
+
+down:
+	docker compose -f docker-compose.dev.yml down
+
+logs:
+	docker compose -f docker-compose.dev.yml logs -f
+
+# Database
+migrate:
+	docker compose -f docker-compose.dev.yml exec backend alembic upgrade head
+
+seed:
+	docker compose -f docker-compose.dev.yml exec backend python -m app.db.seed
+
+backup:
+	cp backend/data/roaauto.db backend/data/backup-$(shell date +%Y%m%d-%H%M%S).db
+
+# Testing
+test:
+	docker compose -f docker-compose.dev.yml exec backend pytest tests/ -v
+
+# Shell access
+shell-backend:
+	docker compose -f docker-compose.dev.yml exec backend bash
+
+shell-frontend:
+	docker compose -f docker-compose.dev.yml exec frontend sh
+
+# Production
+prod-build:
+	docker compose build
+
+prod-up:
+	docker compose up -d