Clarify JWT_SECRET placeholder in configuration files

README.md

@@ -55,7 +55,7 @@ services:
     ports:
       - "3000:3000"
     environment:
-      JWT_SECRET: RANDOM_SECRET
+      JWT_SECRET: RANDOM_SECRET # Replace with a secure random string
       DATABASE_URL: "postgresql://postgres:postgres@db:5432/postgres"
     depends_on:
       - db