chore: initial project setup with backend, frontend, and infrastructure

Add complete NexaPantry application structure including:
- Docker Compose configuration with PostgreSQL, Redis, FastAPI backend, worker, frontend and Caddy
- Environment configuration template with database, auth, and service settings
- GitHub Actions CI workflow for backend/frontend linting, testing, auditing and Docker builds
- AGPL-3.0 license and comprehensive README with setup, development, and security documentation
- Backend

scripts/backup.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env sh
+set -eu
+
+cd "$(dirname "$0")/.."
+mkdir -p backups
+docker compose exec postgres pg_dump -U "${POSTGRES_USER:-nexapantry}" "${POSTGRES_DB:-nexapantry}" > "backups/nexapantry-$(date +%Y%m%d-%H%M%S).sql"
+