refactor: remove embedded MySQL from docker-compose, use external data source

docker-compose.yml

@@ -1,38 +1,19 @@
 services:
-  mysql:
-    image: mysql:8.0
-    environment:
-      MYSQL_ROOT_PASSWORD: ${MYSQL_PASSWORD:-pr_helper_pass}
-      MYSQL_DATABASE: ${MYSQL_DATABASE:-pr_helper}
-    volumes:
-      - mysql-data:/var/lib/mysql
-    ports:
-      - "3306:3306"
-    healthcheck:
-      test: ["CMD", "mysqladmin", "ping", "-h", "localhost"]
-      interval: 10s
-      timeout: 5s
-      retries: 5
-    restart: unless-stopped
-
   pr-helper:
     build: .
     ports:
       - "8080:8080"
     volumes:
       - pr-helper-data:/app/data
+    env_file:
+      - .env
     environment:
       - GIN_MODE=release
-      - MYSQL_HOST=mysql
-      - MYSQL_PORT=3306
-      - MYSQL_USER=root
-      - MYSQL_PASSWORD=${MYSQL_PASSWORD:-pr_helper_pass}
-      - MYSQL_DATABASE=${MYSQL_DATABASE:-pr_helper}
-    depends_on:
-      mysql:
-        condition: service_healthy
+      # MYSQL_HOST in .env should point to your external MySQL
+      # Use host.docker.internal to reach the host machine from inside Docker
+    extra_hosts:
+      - "host.docker.internal:host-gateway"
     restart: unless-stopped
 
 volumes:
-  mysql-data:
   pr-helper-data: