feat(01-06): add docker-compose.yml with postgres:16 for local dev

- Single postgres service pinned to postgres:16
- Credentials recipe/recipe/recipe match application.conf HOCON defaults
- Named volume recipe-pgdata for persistence across restarts
- Healthcheck via pg_isready enables docker compose up --wait usage
- No version key (modern compose v2); Authentik stays on homelab (D-17)

docker-compose.yml

@@ -0,0 +1,20 @@
+services:
+  postgres:
+    image: postgres:16
+    container_name: recipe-postgres
+    environment:
+      POSTGRES_DB: recipe
+      POSTGRES_USER: recipe
+      POSTGRES_PASSWORD: recipe
+    ports:
+      - "5432:5432"
+    volumes:
+      - recipe-pgdata:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U recipe -d recipe"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+
+volumes:
+  recipe-pgdata: