chore(infra): port 9000, make help, db skip-check, Vite CSS fix

- Django dev server now runs on :9000 (was :8000)
- `make` without args shows all targets with descriptions
- `make db` skips docker start if :5432 already reachable (nc check)
- `make seed` and `make superuser` added as explicit targets
- vite.config.js: assetFileNames without hash so static/dist/main.css
  matches the {% static 'dist/main.css' %} reference in base.html
  (run `npm run build` once after checkout to regenerate the CSS file)

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

Makefile

@@ -1,30 +1,43 @@
-.PHONY: dev db migrate shell test lint css createsuperuser collectstatic
+.PHONY: help db dev css seed migrate test lint shell superuser collectstatic
 
-db:
-	docker compose -f docker-compose.dev.yml up -d 2>/dev/null || echo "DB already running"
+.DEFAULT_GOAL := help
 
-dev:
-	uv run manage.py runserver 0.0.0.0:8000
+help: ## List available make targets
+	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) \
+		| awk 'BEGIN {FS = ":.*?## "}; {printf "  \033[36m%-16s\033[0m %s\n", $$1, $$2}'
 
-css:
+db: ## Start PostgreSQL via Docker (skips if already reachable on :5432)
+	@if nc -z localhost 5432 2>/dev/null; then \
+		echo "✓ DB bereits erreichbar auf :5432 — kein Docker-Start nötig"; \
+	else \
+		docker compose -f docker-compose.dev.yml up -d; \
+	fi
+
+dev: ## Start Django dev server on :9000
+	uv run manage.py runserver 0.0.0.0:9000
+
+css: ## Start Tailwind CSS watcher (Vite, rebuild on change)
 	npm run dev
 
-migrate:
+seed: ## Load dev seed data — users, one Ausschreibung, Lose, etc. (idempotent)
+	uv run manage.py seed_dev
+
+superuser: ## Create a Django superuser for /admin/ access
+	uv run manage.py createsuperuser
+
+migrate: ## Generate and apply all pending migrations
 	uv run manage.py makemigrations
 	uv run manage.py migrate
 
-shell:
-	uv run manage.py shell_plus 2>/dev/null || uv run manage.py shell
-
-test:
+test: ## Run the full pytest test suite
 	uv run pytest
 
-lint:
+lint: ## Run ruff (style) and mypy (types)
 	uv run ruff check .
 	uv run mypy vergabe_teilnahme/
 
-createsuperuser:
-	uv run manage.py createsuperuser
+shell: ## Open a Django shell (shell_plus if available)
+	uv run manage.py shell_plus 2>/dev/null || uv run manage.py shell
 
-collectstatic:
+collectstatic: ## Collect static files into staticfiles/ (production step)
 	uv run manage.py collectstatic --noinput