feat(infra): add staging environment setup with docker-compose and scripts

docker-compose.staging.yml

@@ -0,0 +1,28 @@
+version: "3.8"
+
+services:
+  frontend:
+    container_name: staging-gravl-PLACEHOLDER-frontend
+    networks:
+      - staging-network
+    environment:
+      - VITE_API_URL=http://localhost:3001
+      
+  backend:
+    container_name: staging-gravl-PLACEHOLDER-backend
+    networks:
+      - staging-network
+    environment:
+      - NODE_ENV=staging
+      - PORT=3001
+      - CORS_ORIGIN=http://localhost:5173
+    
+  db:
+    container_name: staging-gravl-PLACEHOLDER-db
+    image: postgres:15-alpine
+    networks:
+      - staging-network
+
+networks:
+  staging-network:
+    driver: bridge