feat: PostgreSQL 17 вместо SQLite

pg + connect-pg-simple, async routes, docker-compose, скрипт setup-postgres.

Co-authored-by: Cursor <cursoragent@cursor.com>

docker-compose.yml

@@ -0,0 +1,22 @@
+services:
+  postgres:
+    image: postgres:17
+    container_name: shop-postgres
+    restart: unless-stopped
+    environment:
+      POSTGRES_USER: shop
+      POSTGRES_PASSWORD: shop
+      POSTGRES_DB: shop
+    ports:
+      - '5432:5432'
+    volumes:
+      - shop_pg_data:/var/lib/postgresql/data
+      - ./postgres/init:/docker-entrypoint-initdb.d:ro
+    healthcheck:
+      test: ['CMD-SHELL', 'pg_isready -U shop -d shop']
+      interval: 5s
+      timeout: 5s
+      retries: 5
+
+volumes:
+  shop_pg_data: