- compose.yml: add postgres service with profiles, healthcheck, pg_isready
- compose.yml: add DATABASE_URL env var and conditional depends_on (required: false)
- compose.yml: add postgres-data volume; default deploy remains SQLite-only
- compose.dev.yml: add postgres service with port 5432 exposed for local dev
- compose.dev.yml: add DATABASE_URL env var and conditional depends_on
- pkg/diunwebhook/postgres_test.go: build-tagged NewTestPostgresServer helper
- Introduced `compose.yml` for deployment, pulling the image from the registry
- Added `compose.dev.yml` for local development, building the image from source
- Updated `README.md` and `.claude/CLAUDE.md` with instructions for both configurations
- Introduced `DB_PATH` environment variable to customize SQLite database file location
- Updated `main.go` to use `DB_PATH` with a default fallback (`./diun.db`)
