Tidy up environment variables for local dev

Re autonomic-cooperative/astro-payload-template#2

docker-compose.yml

@@ -27,8 +27,8 @@ services:
     environment:
       DEV: 1
       NAME: ${NAME}
-      PAYLOAD_URL: ${PAYLOAD_URL}
       NODE_ENV: development
+      PAYLOAD_URL: "http://localhost:${PAYLOAD_PORT}"
       PAYLOAD_PORT: ${PAYLOAD_PORT}
       PAYLOAD_SECRET: ${PAYLOAD_SECRET}
       MONGODB_USER:
@@ -39,8 +39,10 @@ services:
     volumes:
       - ./payload/src:/base/src
       - ./astro/src/types.ts:/types.ts
+    volumes:
+      - payload_media:/prod/dist/media
     ports:
-      - 3001:3001
+      - ${PAYLOAD_PORT}:${PAYLOAD_PORT}
     networks:
       - front
       - back
@@ -69,3 +71,4 @@ networks:
 
 volumes: 
   mongo:
+  payload_media: