update .env.example and docker config

backend/.env.example

@@ -1,3 +1,9 @@
-DATABASE_URL=postgresql+asyncpg://codetutor:codetutor@localhost:5432/codetutor
+# Database connection - REQUIRED
+# Format: postgresql+asyncpg://USER:PASSWORD@HOST:PORT/DATABASE
+DATABASE_URL=postgresql+asyncpg://user:password@localhost:5432/codetutor
+
+# Debug mode (optional, default: false)
 DEBUG=false
+
+# CORS allowed origins (optional, default: ["http://localhost:3000"])
 CORS_ORIGINS=["http://localhost:3000"]

docker-compose.yml

@@ -3,15 +3,15 @@ services:
     image: postgres:16-alpine
     container_name: codetutor-db
     environment:
-      POSTGRES_USER: codetutor
-      POSTGRES_PASSWORD: codetutor
-      POSTGRES_DB: codetutor
+      POSTGRES_USER: ${POSTGRES_USER:-codetutor}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:?POSTGRES_PASSWORD is required}
+      POSTGRES_DB: ${POSTGRES_DB:-codetutor}
     ports:
-      - "5432:5432"
+      - "127.0.0.1:5432:5432"
     volumes:
       - codetutor-db-data:/var/lib/postgresql/data
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U codetutor"]
+      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER:-codetutor}"]
       interval: 5s
       timeout: 5s
       retries: 5
@@ -22,7 +22,7 @@ services:
       dockerfile: Dockerfile
     container_name: codetutor-backend
     environment:
-      DATABASE_URL: postgresql+asyncpg://codetutor:codetutor@db:5432/codetutor
+      DATABASE_URL: postgresql+asyncpg://${POSTGRES_USER:-codetutor}:${POSTGRES_PASSWORD}@db:5432/${POSTGRES_DB:-codetutor}
       CORS_ORIGINS: '["http://localhost:3000"]'
     ports:
       - "8000:8000"